Entomostraca.] 



MUSEUM OF ANIMATED NATURE. 



327 





We shall pursue the outline of these crustaceans 

 by observations on the pictorial specimens before 

 us, leaving our reader to adopt either of the above 

 arrangements, of which that eiven b)' Milne Ed- 

 wards is generally preferred. Fig. 3273 is the Biine 

 shrimp or Brine norm (Branchipus stagnalis, Can- 

 cer salinus, Linn.). This singular little creature is. 

 about half an inch in length, and very transparent. 

 It abounds in myriads in the brine pans at Lyming- 

 ton, in which the water contains about a quarter of 

 a pound of salt to a pint of fluid. It is also ibund 

 in some of the salt lakes in Siberia. It swims 

 about with great rapidity, and is in continual 

 motion, revelling in a solution of salt so concen- 

 trated as to destroy most marine creatures instantly. 

 The workmen at the Lymington salterns consider 

 this little shrimp as essential to the purity of the 

 water, and are anxious to promote their increase. 

 These crustaceans undergo remarkable changes in 

 their progress from the egg to maturity, as was 

 observed by Mr. Thompson, whose valuable account 

 is published in the ' Zool. Researches' for 1834. 

 Relerring to Fig. 3273 : — A exhibits the male 

 magnified : a a, composite or network eyes ; b, an- 

 tennae ; c e, mandiluiliforra horns; <i d, proboscidi- 

 form moveable tentaciila rolled spiially ; e, simple 

 ludimentary eye : ff, leaf-like natatory feet ; g, es- 

 sential paits; h h, tail ; i i, terminating filaments: 

 B, front view of head : C, tail of female ; k, egg- 

 pouch ; I, end of egg-duct : D, a young specimen 

 after the first moult. 



Among the Phyllopodous Entomostraca is the 

 penns Apus, of which the Apus productus. Fig. 

 327C, is an example. We have already referred to 

 it in our observations on the Trilobites. These 

 little creatures (Monoculus, Linn.) are found in 

 ponds and ditches, where they often swarm in 

 myriads, and have been known to be carried up by 

 violent storms of wind and scattered over the 

 land ; hence they often appear suddenly in acci- 

 dental rain-water puddles, and in water where none 

 have been previously, especially in the spring and 

 commencement of summer. Their food consists 

 principally of tadpoles ; they swim well on the 

 back, and when they bury themselves in the mud 

 they keep the tail elevated. On exclusion from 

 the egg, the young have only a single eye, and 

 four oar-like limbs ; the body is tailless, and the shell 

 forms a simple undivided carapace. The perfect 

 form is obtained by .successive moults. These 

 creatures are the common food of the Wagtails 

 (Motacilla). 



We may next allude to that curious little micro- 

 scopic creature the Daphnia Pulex, often present 

 ■ in slasnant waters in such myriads congregated 

 together as to give the water the colour of blood. 

 Their moults are very frequent, and the females 

 produce several generations in the course of the 

 summer. All are supposed to perish when the 

 frost of winter sets in, but the eggs remain un- 

 injured and are hatched by the genial warmth 

 of spring, the pools becoming suddenly replete 

 with countless swarms of these active animalcules. 



Another singular species, the Cyclops vulgaris. 

 Fig. 3277, remarkable far the transformations it 

 undergoes, is common in fresh water. On each 

 •ide ol the tail of the female is a pellucid oval 

 sac, filled with eggs, the number of which increases 

 i»ith age ; these sacs are replenished eight or ten 

 times in the course of three months; and as the 

 female begins to lay at an early age, supposing 

 the average number of eggs to be forty each 

 time, the multitude of which a single individual 

 will during six months be the progenitor is enor- 

 mous. The young at their liirth have only four 

 feet, and the body is rounded and tailless ; in 

 due time other limbs appear, and after a lew moults 

 the tail is developed. The eye is single. 



These animalcule-i resist cold with singular power ; 

 they have been frozen in water congealed by ice, 

 which on melting was full of them active as ever ; 

 some however perished. They will also endure 

 to be dried, but not for many minutes. Jurine 

 found that out of twelve individuals dried for 

 fifteen minutes, five only recovered on being re- 

 Stored to the water ; and that of twelve kept dry for 

 twenty-five minutes, all perished. 



Yet as in seasons of drought the pools and ditches 

 aredried, it is most probable that they will retain life 

 buried in the mud as lone as any moisture remains. 

 The eggs, according to Strauss, do not perish, even 

 should the parents, but become hatched in the 

 course of lour or five days when the pools are re- 

 plenished. These creatures grow and change their 

 shells or transparent horny investment like the crab 

 or lobster, the frequency of the exuviations depend- 

 ing on the season of tlie year and the gradual 

 development of the body. The change of the shell 

 IS very complete; not only does the investment of 

 the body become thrown of!', but the outer layer 

 of the fine branchise and the minutest hairs on 

 the antennip. This species is about eight-twelfths 

 •f a line in length, and is subject to several varia- 



tions of colour, being reddish, greenish, or grey. 

 Referring to the figure (3277), A represents the 

 male ; B, the female ; a a, antenna; ; b b, parts at 

 the base of the tail in the male ; d rJ, internal egg- 

 organs: c c, external egg-sacs: C, female, variety : 

 D, a younir Cyclops. 



Fig. 3278 represents Zoea clavata. This sin- 

 gular animalcule is affirmed by Mr. Thompson 

 to be the young of a species of crab, after ex- 

 clusion from the egg. He states that in several 

 genera, as Cancer, Carcinus, Portunus, &c., ob- 

 served by himself, the young appears under this 

 form. On the contrary Rathke, Milne Edwards, and 

 Mr. West wood deny the correctness of Mr. Thomp- 

 son's observations. (See the ' Zool. Journal,' vol. v.) 

 The question is still in abeyance. 



In the genus Cypris, the animal is inclosed in a 

 minute transparent bivalve shell, of a horny tex- 

 ture, and not unlike that of a mussel in miniature; 

 the two valves are united by a hinge, and capable 

 of being closed so as to secure the inhabitant. The 

 animal has six limbs, and two long setaceous an- 

 tennse. These creatures inhabit fresh waters and 

 gently-running streams, and swim with more or less 

 celerity as they bring the filaments of the antennse 

 info play, and the two anterior limbs. They are 

 capable also of creeping over the leaves of aquatic 

 plants. Whether they undergo any metamorphosis 

 is very doubtful ; the eye is single. Their food 

 consists of dead animal and vegetable matters. In 

 habits and manners they closely resemble the Cy- 

 clops, and remain torpid in the moist mud during 

 the droughts of summer, regaining their activity 

 when the rains set in. 



The Cypris ornata. Fig. 3279, is about a line or 

 little more in length; its shell is yellowish green, 

 with pure green bands commencing at the eye. A, 

 a side view of the shell magnified ; B, a view of the 

 hinge. 



Fig. 3280 represents a smaller species, Cypris 

 fusca, with one shell removed to show the internal 

 organization : a a, the outline of the valve ; b, the 

 origin of the hinge membrane : c, the eye ; d d, 

 antennae deprived of their bristles ; e, feet of the 

 first pair ; /, feet of the second pair ; gr, of the third 

 pair ; h. the tail, used for cleaning out the inside of 

 the shell; i, labrum ; k, mandible; /, feeler; m, 

 jaw of the first pair; n, of the second pair; o, 

 branchia ; p q, posterior portion of the egg-sac ; r, 

 insertion of a tubular vessel. 



We now pass to the suctorial crustaceans, crea- 

 tures which have the mouth adapted for sucking the 

 juices which they obtain from other animal bodies; 

 they are thereibre essentially parasitic ; their forms 

 are extremely variable, and all appear to undergo se- 

 veral transformal ions in their progress from their birt h 

 to maturity. The Araneifbrm species, or Pychnogo- 

 nids, are by many referred to the Arachnid.*, or spi- 

 ders, and if is not without doubt that Milne Edwards 

 places them within the pale of the Crustaceans ; they 

 have, however, no tracheae, or pulmonary sacs, the in- 

 teguments most probably serving the office of bran- 

 chiae. These creatures are of small size, with long 

 limbs, and a body divided into segments. 'Ihey mostly 

 take up their abode under stones along the coast, in 

 the water, and sometimes they are said to be found 

 hooked on to fish or other marine animals. 



Fiar. 3281 represents the Pychnogonum littorale 

 magnified : a, one of the hooked feet still more 

 enlarged. 



To the Siphonosfomatous group is referable that 

 curious parasite Caligus Mulleri, Fig. 3282, found 

 adhering to the gill-covers of the codfish. It holds 

 on by means of the hooks which terminate the an- 

 terior pairs of limbs; and beneath the head is an 

 obtuse beak, throueh which it sucks up its nourish- 

 ment. The terminal prolongations are by some 

 supposed to fulfil the office of branchiaj. 



Another form is exhibited by the Phyllophora, 

 remarkable for the lamellar appendages with which 

 the back is covered. These creatures, like many 

 others allied to them, live upon fishes, but not per- 

 manently ; they can let go their hold and change 

 their place either by swimming or slowly crawling ; 

 Fie 3283 represents the Phyllophora cornuta, from 

 Toneatahoo : o, the under surface. 



Passing over numerous genera, we come to the 

 Lerneiform section, remarkable for the singularity of 

 their appearance. When young they resemble the 

 young of Cyclops, and are then provided with a 

 frontal eye and natatory limbs, swimming with fa- 

 cility ; but havinsr undergone a certain number of 

 moults, they cease to lead an erratic life. The 

 limbs, now no longer needed, become lost, or waste 

 away, the eye mostly disappears, and the body as- 

 sumes a strange form. The female is at this stage 

 found fixed to some fish or aquatic animal, with the 

 male clinging closely to her. They are soldered, 

 as it were, to their victim by means of various cu- 

 taneous appendages, or, in some cases, moveable 

 arms. 



Fig. .3284 represents a species of Chondr.icanthus 

 (Ch. cornutus) found on various kinds of flat-fish: 



[ a, the female magnified, with the double egg-sac, 

 b, the male in profile, highly magnified ; c, the 

 same seen Irom below; d, the head of the female 

 seen from below ; e, the mouth. 



A still more remarkable form is found in Ach- 

 theres, Tracheliasfes, &c. They are covered with n 

 dense horny but transparent investment. In the 

 females the thorax gives origin to two large arms, 

 which bend forwards like horns, and meet, the 

 points united together forming a cup-like sucking 

 disc. There are two pairs of hooked jaw-feet for 

 close adhesion. The achtheres is found on the perch, 

 and is not a quarter of an inch in length. The Tra- 

 cheliastes polycolpus, Fig. 3283, is found on the fins 

 of the chub: «, the female magnified seen from 

 above, with the two egg-sacs ; b, the same seen 

 laterally and deprived of the egg-sacs; c, the ante- 

 rior extremity of the body more highly magnified ; 

 rf, appendage representing the second pair of hooked 

 jaw-feet ; e, mandible : J, the first stage of this ani- 

 mal ; g, the same in the second stage. 



Passing by Leinaa, Lerneocera, Penclla,* &c., 

 we pause at Lerneonema. Of this genus one spe- 

 cies, Lerneonema monilaris. Fig. 3286 (magnified), 

 is Ibund attached to the eye of the sprat. The 

 whole head of the parasites of this and several allied 

 genera is plunged into the tissue of the sufterer, 

 and retained, like an arrow, by barbs or horny pro- 

 longations. 



Fig. 3287 shows several of these creatures (the 

 Lernica spratti of Mr. Sowerby) attached to the fish 

 in question. The Lerneonema monilaris, or sprat 

 Lernaea, is luminous at night ; the fishermen state 

 that a shoal is often headed by several fish thus 

 infested, and they call them Lanthorn Sprats. 



Here we close our sketch of the suctorial Crustacea 

 as arranged by Milne Edwards. Cuvier places the 

 Lerneans among his Vers intestinaux cavitaires, and 

 other anatomists in a class to which they give the 

 title of Epizoa, in allusion to their external parasitic 

 mode of life ; and though we have here adopted 

 Milne Edwards* arrangement, we think the class 

 Epizoa to be founded upon solid grounds. It may 

 be observed that in Cuvier's arrangement the little 

 Nicothoe, so abundant on the gills of the lobster, is 

 placed among the Siphonostomata. 



There is a most interesting group of crustaceans, 

 constituting a distinct subclass, which we have 

 purposely refrained from describing. It is termed 

 by Milne" Edwards the 



SUBCLASS XIPHOSURA. 



In this curious form we find the haunches or basal 

 joints of the thoracic limbs bristling with short stout 

 spines, serving the office of jaws lor crushing and 

 grinding the food forced by their action into the 

 mouth, which they surround. If we look at one of 

 these strange crabs from above, we see no limbs, 

 all being covered by a very convex buckler, divided 

 into two parts, viz., a cephalo-thoracic buckler, and 

 an abdominal buckler, to which is added a long 

 caudal spine. The first buckler is rounded in front, 

 and deeply notched posteriorly lor the reception 

 of the base of the abdominal shield, which is ser- 

 rated along each side, each interval between the 

 teeth having a moveable spine. Tlie eyes are four 

 in number, two large and oval, with numerous fa- 

 cets situated laterally each on the outer side of a 

 kind of broad median keel on the first buckler: the 

 two other eyes are simple, small, and placed close 

 together at the anterior extremity of the keel. 



The thoracic limbs consist of six pairs; the first 

 pair are much smaller than the others and placed 

 anteriorly to the mouth. The subsequent limbs are 

 well developed, and all terminating in pinceis, ex- 

 cepting the foremost pair of the.se in the males, 

 which end in simple points. They are composed of 

 six joints, of which the basal ones are armed with 

 spines and serve as jaws; but the basal joint of 

 the sixth pair terminates on the inside in a toothed 

 surface, and carries at its external angle a flabelli- 

 foim appendage. The abdomen is hollowed deeply, 

 and carries six pairs of false feet; of these the first 

 pair are united into one broad valvular pi-ece, which 

 shuts down over the rest so as to protect and cover 

 them. The succeeding false feet are also Ibliaceous, 

 and united together down the median line; they 

 are branchiferous, each foot cariying on its external 

 edge a large loliaceous gill, formed of cutaneous 

 laminae disposed transversely, and piled one on the 

 other like the leaves of a book. The caudal spike 

 is stout, sharp, and moveable. 



This subclass contains only one generic group, 

 viz. Limulus. The Limuli or Xiphosures undergo 

 great translbrmations in their progress from the egg 

 to nmtuiity; they are natives of the Indian and 

 Japanese seas, and also some parts of the coasts of 

 America, within the northern hemisphere. They 

 frequently come ashore, traversing the flat sandy 

 beaches, and look like self-moving shields, none of 



* The Penella filosa buries itself in the flesli of the swnrdllsli, 

 tunny, Sec, and tolmeuts them horribly, being seven or eight inchaa 

 long. 



