§$ 290. THE CRUSTACEA. 349 
probably, some relation between this remarkable mode of generation and the 
fact that some females lay two kinds of eggs, one of which is developed 
spontaneously, that is, without the influence of sperm, while the other re- 
quires to be fecundated. 
The structure and disposition of the genital organs is so different in the 
various divisions of Crustacea, that it is difficult to make any general state- 
ment about them. Usually, there is a complete duplication of these organs, 
internal and external, with both sexes. With the females, there is nearly 
always, right and left, a longer or shorter, rarely-branched, ovarian tube. 
This is succeeded by a narrow oviduct, usually long, and often flexuous. This 
last continues into a large vagina, which opens at very different points ou 
the ventral surface, sometimes quite in front, sometimes near the middle, 
or at the posterior extremity. It is rare that this vagina has a Receptacu- 
lum seminis ; but, more commonly, the females have special glandular 
canals annexed to the genital orifice. The product of these last is a viscous 
mucus, which hardens in water, and serves to envelop the eggs, and to glue 
them together. The eggs, thus bound together in chaplets or clusters, 
remain glued to the parts neighboring the genital orifice, or to the post- 
abdominal feet, and are borne about by the females, until the embryos 
are fully developed. With other females, where these organs are wauting, 
they are replaced by a special pouch (Marsupzum) situated, usually, at the 
inferior surface of ‘the thorax. In this pouch the egys are deposited and 
remain until their embryos are completely developed. 
With the males, the internal genital organs are disposed in a similar 
manner, and often have the same form as those of the females. A 
careful examination is, therefore, necessary, to perceive their distinctive 
character. Moreover, they open, also, at the most varied points of the 
body. In many species, there are, near the genital orifices, copulatory 
organs in the form of stylets, or canaliculi, which serve to transfer the 
sperm into the female organs. With others, the antennae, or some of the 
feet, are provided with a kind of hook, or pincers, with which they seize 
and retain the females during copulation. Sometimes the internal organs 
of the left communicate, by anastomoses, with those of the right side, or, in 
the place of two lateral genital openings, there is only one, situated on the 
median line. With many species, the genital organs, internal and external, 
are simple, and placed in the axis of the body; but it is rarely observed, 
that the oviducts and deferent canals are single where the ovaries or the 
testicles are double, or that there are two genital openings for single in- 
ternal organs. 
The Eggs of the Crustacea are usually of either a lively green, yellow, 
or violet color. They are always spherical, and composed of a dense 
chorion, containing a vitellus, which surrounds a germinative vesicle, with 
one or more nuclei. The vitellus is composed of numerous oil-globules, 
which are held together by a clear, albuminous liquid, and give the egg its 
peculiar color. 
The sperm is white and sometimes opalescent. The spermatic particles 
are of very varied and remarkable forms. Nearly always, they are 
2 This phenomenon is undoubtedly analogous to mal. Crust. generat., 1844,.and his Bemerkungen in 
that of the alternation of generation, which isso Froréep’s neue Notiz. XXIV. 1842, p. 181 ; Erdd, 
general with the other lower animals. Entwickelung d. Hummereies, p. 13 ; and especially 
8 For the eggs of Crustacea, see Rathké, De Ani- Wagner, Prodromus, &c., p. 8, Tab. I. fig. 12-17. 
30 
