^292. 



THE CRUSTACEA. 



353: 



shell and the posterior part of the back.<^^ The females of Daphnia have, 

 beside those eggs which are rapidly developed in this cavity, another kind 

 known as the hibernating eggs, and in which no gerniinative vesicle is 

 observed. They are always found in couples in a thickened, saddle-like por- 

 tion of the shell of the animal, which is often of a black color, and separ- 

 ated from the shell by a kind of moulting. Thus enveloped in a bivalved 

 capsule, they are protected against the severities of the winter.^'** 



Among the Phyllopoda, the Apodidae are distinguished for the very large, 

 multiramose, ovarian follicles which border the two oviducts on every side ; 

 these last are straight and large, and situated on the side of the digestive 

 canal. With Apus, each of them sends oiF, at about its middle, a short,, 

 excretory canal, to the eleventh pair of feet, in which there are two alveo- 

 late receptacles with covers for the reception of the eggs.'"' With the- 

 Branchiopoda, the ovaries consist of two straight eoeca, situated in the- 

 tail, on each side of the intestine. Their upper extremity, beneath the last 

 pair of feet, passes into an elongated receptacle. These two receptacles, 

 separated from each other only by a thin partition, have a narrow outlet at 

 their posterior extremity, and form, under the base of the tail, a kind of 

 oblong tumor, into which the hard and granular eggs are constantly cast 

 from the contractions of special muscular bands.'''' There are, moreover^ 

 on the sides of the body "ibovethe last pair of feet, two oblique horny 

 plates, which the males, during copulation, seize with their cephalic pincers. 



With the Poecilopoda, the cephalothorax contains two ramified ovaries,. 



3 See Straus, Mem. sur les Daphnia, loc. cit. p. 

 413, Fl. XXIX. and Jurine, Hist. d. Monocl. PI. 

 VIII.-XVI. The genera Argulus and Cypris dif- 

 fer, moreover, from the other Entomostraca, in 

 that they do not bear about tlieir eggs after laying, 

 but deposit them on foreign bodies ; see Jurine, 

 Mem. sur I'Argule, loc. cit. p. 451, and Straus, 

 Mem. sur les Cypris, loc. cit. p. 54. 



< The formation of the saddle, which is intimate- 

 ly connected with the deposition of the hibernating 

 eggs, has been called by Jurine the Mnladie de la 

 seile. But it has been before observed by Müller 

 (Entomostr. p. 84, Tab. XI. fig. 9-11, Tab. XII. 

 fig. 5), and by Ramdohr (loc. cit. p. 28). See, also, 

 Straus, lue. cit. p. 415, PI. XXIX. fig. 16, 17, and 

 Jurine, Hist. d. Monocl. p. 120, PI. XI. fig. 1, 4.* 



5 Sec Schaeffer, Der krel^sartige Kiefenfuss, p. 

 79, Taf. IV. tig. 2-7, and Zaddach, loc. cit. p. 51, 



Tab. I. {Apus). With Limnadia, and Isaura, a 

 special receptacb is wanting ; the eggs are attached 

 to the feet probably by the aid of their hairy 

 e.xternal envelope ; see Brongniart, loc. cit. p. 88 } 

 Straus, Mus. Senckenb. loc. cit. Taf. VII. fig. 16,. 

 and Joly, loc. cit. p. 308, PI. I.X. A.f 



6 See Prevost, iujurine's Hist. d. Monocles, p. 

 228, PI. XX. tig. 1, 10 (C/iirocephalus). This .au- 

 thor erroneously declares, moreover (loc. cit. p- 

 207), tliat the females of this animal have, also, at 

 the end of the tail, openings into wliich the sperm is 

 received during coition. See also Joly (loc. cit. p. 

 240, PI. VII. tig. 12, PI. VIII. fig. 4), who regards 

 tlie receptacles of the eggs, with Artemia, as the 

 ovaries. The eggs with a solid, granular shell, of 

 Branchipus, have been pretty distinctly figured by 

 Schaejf'er (Der tischform. Kiefenfuss, tig. 14). 



* [ § 292, note 4.] Recent investigations upon the 

 economy and development of the Crustacea indi- 

 cate that the phenomena above-mentioned, of the 

 reproduction by means of a second kind of eggs 

 (so-called), is far from being limited to a few of 

 these animals. Indeed, it is probable that all or 

 most of the Entomostraca reproduce by this mode. 

 As mentioned on a preceding page, these phenome- 

 na do not appear to me to belong to true oviparous 

 reproduction, but must be considered as a kind of 

 internal gemmiparity. The so-called winter-eggs 

 are, therefore, not eggs, but buds {gemmae) — a 

 view which is borne out by their composition, — 

 there being no germinative vesicle and dot. This 

 subject will be discussed with some detail below (note 

 under §355) when speaking of the Aphides— animals 

 with which I have traced these phenomena with 

 some care. For many interesting details on this 



3U* 



subject, see LiSvin, Die Branchiopoden der Dan- 

 ziger Gegend, 1848, p. 11. et seq.; Baird, Brit. 

 Entomostr. &c. loc. cit. passim ; Zenker, Physiot- 

 ogische Bemerkungen über die Daphnoidae, in 

 Müller''s Arch. 1S51, p. 112 ; Leydig, lieber Ar- 

 temia salina und Brancliipus stagnalis, in Siebold 

 and KöUiker's Zeitsch. III. 1851, p. 297. — Ed. 



t [ § 292, note 5.] For the female genital organs- 

 of Arteinia and Branchipus, see Leydig (loc. cit. 

 Siebold and Kölliker''s Zeitsch. III. p. 300). Jo- 

 ly, it would appear, did not observe the ovaries of 

 Artemia, but has described the egg-capsules as 

 such. The real ovaries here consist of sacs or 

 pouches, lying near the dorsal surface of the abdo- 

 men, and extending to the second abdominal ring ; 

 these ovarian sacs pass into a vesiculiform dilata- 

 tion, which has non-muscular walls, and corre- 

 sponds to a uterus. — Ed. 



