124 CRUSTACEA. 



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 (esophagus by a straight canal, that he sus- 

 pects may be a testis or salivary gland. The individuals which 

 were the subjects of these observations having ovaries, the Cy- 

 pridcs 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 gene- 

 ration(l). 



According to Jurine, the antennx 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 

 motionsj 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 termi- 

 nated by a long hook, or the penultimates, then support the body. 

 He supposes that those which, according to him, form the second 

 pair, are destined to create an aqueous current and to direct it to- 

 ward the mouth, thereby assimilating their functions to those of 

 the second inferior antennse, which he calls antennula. The two 

 threads composing the tail unite on leaving the shell, and seem to 

 form but onej they serve, as he supposes, to brush out its interior. 

 The female deposits her ova in mass, fixing them on plants or the 

 mud by means of gluten. During this operation, which lasts about 

 twelve hours, and in the largest species produces twenty-four eggs, 

 she clings with her second feet, and in such a manner as not to fear 

 the shock of the water. He collected some of these packets of 

 newly laid eggs, and after separating them, observed the hatching 

 of the young ones, and obtained a second generation without the in- 



(1) See the alimentary canal of the Daphnia pulex, figured by Jurine, X, 7, and 

 Randohi', Monoc, Tab. V, ii, d, d, and x. 



