442 



CRUSTACEA. 





, in (liircrcut stages. 



Artemia saUna, (Cancer salinus, Linn., Montague, in Trans. Linn. Soc, 9. pi. 14,) [the Brine Shrimp] is a very 

 small Crustaceous animal, commonly found in the salt pans at Lymington, in England, when the evaporation 

 of the water is considerably advanced. [Latreille observed that we were in possession of very imperfect 

 characters of this little species. More recently, however. Dr. J. V. Thompson has minutely examined its struc- 

 ture, and has traced the gradual developement of this singular animal, which, when full grown, is about half 



an inch in length, with a highly polished surface. " Nature having con- 

 structed them with members solely adapted for swimming, they seem 

 to be in perpetual quest of prey, gliding with an almost even motion 

 through the water, and moving with equal indifference and facility 

 on the back, belly, and sides ; the shape of the animal, the undu- 

 lating movements of its fins, and the glossy appearance of its coat, 

 renders it an object of a very interesting description." — Thompson. M. 

 V. Audouin has published some additional and equally interesting 

 details of it in the Annates des Sciences Naturelles for 1837.] 



Branchipus, Latr. (Chirocephalus, B. Prevost), have the eyes placed 

 at the end of elongated peduncles ; the body long, narrow, and com- 

 pressed, the head distinct from the thorax, with its organs varying in 

 the sexes, with two horn-like projections between the eyes ; eleven pairs of 

 legs, and the tail terminated by two ciliated, elongated plates. In both sexes the body is nearly filiform, composed 

 of ahead separated from the thorax by a kind of neck, of a thorax channelled beneath, and divided, at least on the 

 upper side, into eleven segments, not including the neck, each of which supports a pair of very compressed bran- 

 chial legs, generally composed of three lamellar joints, with the edges fringed with hairs, and of a long tail, 

 gradually narrowed to the end, composed of nine segments, terminated by two or more less elongated filaments with 

 ciliated edges. The under side of the second segment of the tail exhibits the male sexual organs, and in the female 

 is furnished with an elongated sac, containing the eggs ready to be laid. The head, (of which the organization of 

 the dill^rent parts, especially those of the mouth, requires a more minute investigation than has been given to it 

 by Prevost and Schaffer), presents, 1, two facetted eyes, wide apart, at the end of two flexible peduncles, formed by 

 the lateral prolongation of the head; 2, tv,o frontal antenna; scarcely shorter than the head, slender, filiform, and 

 composed of minute articidations ; 3, two produced organs beneath them, either in the fonn of horns, and 

 composed of a single joint, or finger-shaped and two-jointed ; 4, a mouth on the under side of the head, composed 

 of two kinds of toothed mandibles, destitute of palpi, and of some other pieces. We believe that these produced 

 horns are only appendages (but differently constnicted in the males) of the frontal antennae ; the two other 

 antenna; may either be obliterated in the females, and may constitute in the males of C. diaphanus, Prev., the singular 

 tentacles with teeth, and capable of being rolled up in a coil, which B. Prevost calls the fingers of the hands. 

 The observations of Schaffer upon the hairs of the feet, prove that they are so many aerial canals, and that the sur- 

 face of the feet to which they are attached is able to absorb a portion of the air which is in contact with them, in 

 the form of bubbles. 



Chh-ocephahis diaphanus, B. Prevost, nearly allied to our Branchipus paludosiis, if indeed it be distinct, has, on 

 bursting from the egg, the body divided into two nearly equal and nearly globular masses. The anterior exhibits 

 a sino-le simple eye, two short antennae, two very large oars, ciliated at the end, two short, slender, 5-jointed legs. At 

 the end of the first moulting the two composite eyes appear, the body is gradually elongated, and terminates in a 

 conical, articulated tail, with two filaments at the tip. The subsequent moultings graduaOy develope the legs, 

 and the oar-like appendages disappear. The Branchipi are found, often in great numbers, in small puddles of soft, 

 disturbed water, and often in those formed after heavy rains, especially in autumn and spring. The first frosts 

 destroy them. They generally swim on the back, and their short, lamellar feet, unable to assist in walking, are 

 then kept in an undulatory motion, very agreeable to the sight, and by which a current is produced, which, follow- 

 ing the canal of the breast, bears to the mouth the minute particles of the insect's food. When it swims it violently 

 beats the w ater from right to left with its tail, which gives it sudden jerks. When deprived of a sufficient degree 

 of moisture, it soon ceases to move. The shell of the eggs is thick and strong, which favours their preservation, 

 since it appears that desiccation, unless it be too strong, does not alter the germ, and that the yoimg are subse- 

 quently hatched when a sufficient quantity of rain falls. M. Desmarest has often observed the Branchipus in pud;- 

 dies of fresh rain-water on the summit of the free-stone (gres) of Fontainebleau. Tlie female Chirocephali have 

 several distinct layings of eggs, after a single impregnation ; each operation lasting several hom-s, or even an 

 entire day : each brood consists of from one hundred to four hundred eggs, ten or twelve being discharged at once, 

 with sufficient force to embed them in the sand. The two horns, situated beneath the superior antennae in Branchi- 

 jmspdludosus, are composed, in both sexes, of two joints, the last of which is large and curved in the male, and 

 very short and conical in the female. In Branchipus stagnalis, the 

 horns are composed of but one joint, those of the male resembling, in 

 their form, direction, and teeth, the jaws of the Lucanus Cervus, or Stag 

 Beetle. [There is an interesting memoir on this animal and its trans- 

 formation, by Dr. Shaw, in the Linn<ean Transactions, vol. i.] 



Eulimene, Latr., is destitute of a tail, the body, which is nearly linear, 

 terminating immediately behind the thorax and posterior legs : the four 

 antenna; are short, nearly filiform, two being smaller than the others, and nearly resembling palpi, placed at 

 the anterior extremity of the head. The head is transverse, with two eyes placed upon large cylindrical pedun- 

 cles, eleven pairs of branchial feet, of which the three anterior joints and the terminal one arc smaller, and 



Fig.il.. 



cliiims stagnalis. 



