Introduction to Animal Morphology. 



217 



of ovaries are small, behind the testes, having two 

 wide-mouthed oviducts behind them, attached to the 

 body wall ; with these communicate round sperma- 

 thecal sacs lying near the testes. The oviducts open 

 anteriorly to the penis. In the earthworm six segments 

 in advance of the clitellum are the copulatory, ad- 

 hesive organs, which are modified, imperforate, loco- 

 motor setae. Most other worms have no special 

 genital ducts, but empty the sex-products through the 

 segmental organs. The ova may form on the inner 

 wall of the dissepiments, or of the body cavity 

 (Tomopteris), or in 1-3* pair of ovaries, and the semen 

 in 1-4 pair of testes. Each sex-organ has a vessel or 

 a cellular string in its axis, from which the sperm 

 cells or eggs bud. 



The ova are either single or in clusters Fig. 30. 

 within capsules, cocoon-like in Lumbricus, 

 pillared in Arenicola, with copious or no 

 albumen (Tubifex). A few (Eunicea, Syllis, 

 Cirrhatulus) are viviparous. Lumbricus de- 

 velops directly. Most of the others have in- 

 direct development by a dissimilar larva. 

 This has no gastrseal stage, according to 

 some observers, and may be ciliated at the 

 extremity (Telotrochal), at one end only 

 (Monotrochal as in Polynoe), or at both ends 

 (Amphitrochal as in Terebella), or ciliated in 

 the middle (Mesotrochal as in Spioch^top- 

 terus), or with many wreaths of cilia (Poly- 

 trochal as in Arenicola, Fig. 30). Lysidice has five ciliary 



Polytroclial larva of 

 Arenicola. 



* CEnone diphyllidia has in the side of each ring two little grape-like 

 ovaries, whose connmon oviduct opens at the base of the parapodia. 

 Euphrosyne has symmetrical ovaries extending as winding pouches, opening 

 at the back of the inner edge of the gills. Chloeia has lobed ovaries, each 

 lobe a long pouch. 



