442 



CRUSTACEA. 



Fig. 20.- 



Artcmia saliiia, {Cancer sa/iuus, Linn., Montague, in Trmi-s. Liiiu. Soc, 9. pi- 1^,) [tbe Brine Slirimp] is avery 

 small Crustaceous animal, coininoiily 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 developenient of this singular animal, which, when full grown, is about half 



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

 structed thein with members solely adapted for swimming, they seem 

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

 tlirough the water, and moving with equal inditlereuce 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 avery interesting description."— r/zoy^jyi-on. M. 

 V, Audouin has published some additional and er|ually interr^ling 

 details of it in the Annales des Sciences Nahinslics Un- ISS;.] 



Bra/ic/iipui-, Latr. iCJiirocephaltis, 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 varj'ing 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 ditt'erent 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, two frontal antenna scarcely shorter than the head, slender, liiiform, and 

 composed of minute articulations; 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 liead, composed 

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

 horns are only appendages Qj^it differently constructed in the males) of the frontal antenn<e ; 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 li. Prevost calls the fingers of the hands. 

 The observations of SciiiiHer upon the hairs of the feet, prove that they are so many aerial canids, and tliat the sur- 

 face of the feet to which they are attached is able to ali^orb a iii.irtion uf thu air which is in contact with them, in 

 the form of bubbles. 



Chiroccphalus diaphanus, B. Prevost, nearly allied to oiu- Branchipus paludosus, if indeed it be distinct, has, on 

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

 a single simple eye, t^vo short antennas, two very large oars, ciliated at the end, tw^o short, slender, S-joinii.-il li".;s. At 

 the end of the first moulting the two composite eyes appear, the body is gradually elongated, and tcrnHn.'Ltrs jn a 

 conical, articulated tail, with two filaments at the tip. The subsequent moultings gradually de\cln]ie the legs, 

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

 disturbed water, and often in those formed after hea'\'y' rains, especially in autumn and spring. The first frosts 

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

 then kept in an undulatoi^ 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 water 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 tliiclc and strong, which favours their pi-esen^ation, 

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

 quently hatched when a sufficient quantity of rnin falls. M. Desmarest has often obsen-ed the Branchipus in pud- 

 dles of fresh rain-water on the summit of the free-stone {grits) of Fontainebleau. The female Chirocephali have 

 several distinct layin'jcs of eggs, after a single impregnation ; each operation lasting several hours, or even an 

 entire d,iy ; i;;mI[ Ijiniid consists of from one hundred to fuur luuidred eggs, ten or twelve bein-- ilisrli;irgril ;u unce 

 with sniriiiriil forri; (n L'uibed them in the sand. The two horns, situated beneath the supcrirn- ;Milruii;r in Jjni/irhi- 

 puspaludusus, ai'c composed, in both sexes, of two joints, the last of which is large and cur\rd in the male, and 

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

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

 their fonn, direction, and teeth, the jaws of the Lucauus Cervus^ or Stag 

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

 formation, by Br. Shaw, in the Limiwan Transactions, vol. i.] 



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

 terminating immediately behind the thurax and posterior legs : the four 



antenna^are short, nearly filiform, two bring smaller than the others, and nearly resemlilin- palpi, j-ilnrrd at 

 the anterior extremity of the head. Tin; head is transverse, with two eyes plac-d ii|Mm largr o hndrn.al pcdun 

 cles, eleven pairs of branchial feet, of which the three anterior joints and the terminal imu; arL- smaller, and 



Fig-21.- 



