86 



THE CRUSTACEA 



-ut 



Pieprodudive System. — The ovari/ may be paired or single. It is 

 generally of small size and the ova pass at an early stage into the 

 oviducts, which are large and give otf l)lind diverticula (Fig. 48, 

 lit). In the parasitic forms the ramifications 

 of the oviducts (or uteri) occupy the greater 

 part of the body-cavity, and even, in Chondra- 

 canthus, invade the misshapen thoracic limbs. 

 In the terminal portion of the oviducts the 

 walls are glandular and secrete the cement 

 hy which the eggs when expelled are agglu- 

 tinated together. The openings of the oviducts 

 are on the first abdominal somite, and may 

 be ventral, lateral, or dorsal in position. The 

 genital valves covering the openings have been 

 already mentioned. 



In the great majority of Eucopepoda the 

 female generative ajiparatus possesses another 

 opening or pair of openings on the ventral 

 side of the genital somite, serving for the 

 entrance of the sperm and communicating 

 fenua*irS£'^%Swiia! internally with a single or double spermatheca 

 opening of oviduct; ov, (Fig. 48, sv). On each side the spermatheca 



Fig. 48. 



ovary ; ovd, oviduct ; j), . «■ i . i • i • , -ii ^i, 



copulatory'pore;sj),sperma- glveS Oil a duct wluch COmmuniCatCS With the 



ofovi(^uct:''SfterHaT^^^^^^^ oviduct close to its external aperture. Rarely 

 (Pleuromamma) only one sperm-duct is present. 

 This sperm-duct is lined with chitin, but, in some cases at least, 

 the spermatheca is devoid of such a lining and is difficult to 

 detect except when distended with spermatozoa. It is stated to 

 he altogether absent in Heterocope (Gymnoplea). While the details 

 of this apparatus have been investigated only in a relatively small 

 number of forms, it seems probable that the possession of special 

 copulatory pores apart from the openings of the oviducts is a 

 characteristic of all Eucopepoda. Canii has proposed to divide 

 the order into two groups, Monoporodelphya and Diporodelphya, 

 according as the copulatory pore is single or paired, l)ut it appears 

 from Giesbrecht's researches that the two conditions may be found 

 in closely allied forms. The last-named author has observed that 

 in Scottocheres (one of the Asterocheridae) the sperm -duct opens 

 not into the spermatheca but to the outside by a separate pore 

 close to the opening of the latter. 



The eggs are sometimes deposited singly in the Avater 

 (some Gymnoplea), but in the great majority of the Eucope- 

 poda they are cemented together into packets by means of a 

 secretion formed by the oviduct. In all except a very few 

 cases (Choniostomatidae) these packets are carried by the female 

 attached to the openings of the oviducts until the eggs hatch. 



