246 CRUSTACEA. 



tcrnally, but arc turned up, applied to the posterior sides of the body 

 in order to support the ovaries, and terminate in two very small 

 hooks *. The body presents no distinct articulations, and terminates 

 posteriorly in a kind of soft tail which is doubled underneath, with 

 two conical or setaceous threads furnished with three setae or hooks 

 at the end, directed backwards and issuing from the shell. The 

 ovaries constitute two large, simple and conical vessels forming a 

 cul-de-sac at their origin and situated on the posterior sides of the 

 body, underneath the shell, and opening, side by side, in the ante- 

 rior portion of the abdomen where the canal formed by the tail estab- 

 lishes a communication between them. The ova are spherical. These 

 Crustacea spawn, and change their skin, as frequently as the Cy- 

 clopes and other Entomostraca, and their mode of life is the same. 

 Ledermullcr states, that he observed them in coitu. Modern natur- 

 alists, who have most closely studied them, however, have never 

 been able to discover their sexual organs with certainty, nor been 

 fortunate enough to see them in actu. M. Straus observed, under 

 the origin of the mandibles, the insertion of a stout conical vessel 

 filled with a gelatinous substance, which appeared to communicate 

 with the oesophagus by a straight canal, that he suspects may be a 

 testis or salivary gland. The individuals which were the subjects of 

 these observations having ovaries, the Cyprides according to the first 

 supposition must be hermaphrodites. This is so much the more 

 doubtful, however, as he himself remarks that it is possible the males 

 may only exist at a particular season of the year, and that the vessel 

 alluded to seems to be more nearly connected with the function of 

 digestion than with that of generation f . 



According to Jurine, the antennae are true fins, the threads of 

 which are spread out or united at the will of the animal, and in pro- 

 portion to the degree of velocity it wishes to communicate to its 

 motions; sometimes but a single one is visible, at others they are all 

 displayed. We also think that these threads, and those of the two 

 anterior feet, may be considered as aiding in respiration, quite as 

 much as the laminae of the mandibles and of the two superior jaws, 

 which M. Straus distinguishes by the name of branchial. The last, 

 or those of the jaws, appear to me to be true but greatly dilated palpi, 

 and the two others are appendages of the mandibular palpi. See 

 Jurine, Hist, des Mon. VI, 3. 



According to the naturalist of Geneva before mentioned, these 

 animals, while they are swimming, move their anterior feet as ra- 

 pidly as their antennae, but very slowly when walking over the sur- 

 face of aquatic plants. These feet, conjointly with the two terminated 

 by a long hook, or the penultimates, then support the body. He sup- 

 poses that those which, according to him, form the second pair, are 

 destined to create an aqueous current and to direct it toward the 



* In the figure given by Randohr these feet consist of but three joints, and the 

 last is somewhat dilated and emarginated at the end, with a hook in the middle of 

 the emarfi nation. 



J See the alimentary canal of the Daphnia pulex, figured by Jurine, X, 7, and 

 Randohr, Monoc. Tab. V, ii, d, d, and x. 



