NO. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 29 



27ie female reproductive organs. — In the copepodid stage, when 

 fertilization takes phiee, the ovaries of the female are ovoids or 

 ellipsoids, like the testes of the male, and are similarly situated in 

 the posterior portion of the cephalothorax, near the dorsal surface. 

 The oviducts correspond in every particular with the vasa deferentia, 

 leading back alongside the intestine to an enlargement in the genital 

 segment, \Yhich is to receive the sperms from the spermatophores 

 deposited on the outside of the segment by the male; and in the 

 genus Lcrnaea the posterior portion of the oviduct secretes cement 

 substance, like the vasa deferentia. 



During the retrogressive metamorphosis which follows the fixa- 

 tion of the female to her final host a great change takes place in 

 both the location and structure of the reproductive organs. The 

 ovary migrates from the cephalothorax through the entire length of 

 the free thorax into the genital segment, where it assumes a position 

 near the dorsal surface at the anterior end of the segment, except in 

 the new genus Collipravus, where it is near the posterior end at the 

 base of the abdomen. In most of the genera the ovary also reverses 

 its position, the anterior end becoming posterior and the posterior 

 end anterior, so that the oviducts in the adult always arise from 

 the anterior end. Furthermore, in some genera {Lernaeocera., Pen- 

 nella, etc.) the two ovaries move inward toward the midline and 

 finally come together and fuse, leaving only a pair of anterior and 

 posterior horns to mark their dual origin. 



The oviducts noAv pass down around the intestine to the ventral 

 surface and strait back to the vulvae without convolutions, except 

 in Pennella, where there is a single fold just as they leave the ovaries. 



A pair of cement glands is also formed, whose anterior glandular 

 portion originates at the anterior end of the genital segment at the 

 base of the neck and ventral to the oviducts. Each gland is cylin- 

 drical and without convolutions, and the two lie side by side along 

 the midline. At about its center each gland is contracted and passes 

 into a duct which empties into the oviduct of the same side just inside 

 the vulva. These ducts are also without convolutions in all the 

 genera except Lernaeolophus and Lernaeocera^ in which they are 

 vertically convoluted. 



In the genus Lernaea the cells at the posterior end of the ovary 

 gi'adually loosen themselves from the epithelium and become asso- 

 ciated in longer oi* shorter filaments or strings, each of which is 

 made up of many cells flattened together like a roAv of coins and 

 which increase in size toward the anterior end of the ovary and there 

 break up into separate eggs as they pass into the oviducts, the con- 

 ditions being thus similar to those found in the Lernaeopodidae. 



In all the other genera thus far studied the ovary consists of a 

 mass of tiny nucleated cells, with no arrangement into filaments or 



