IV 



VERMES— GENITAL ORGANS 



263 



masses between the branches of the intestine, especially on the dorsal 

 side. These masses of eggs are regarded as ovaries. It is, however, 

 possible that they consist of eggs which have left the real ovaria. 



Fig. 176. — Section tlirougli Myzostoma, after v. Graff, ov, Ovaries ; cto, intestinal branches ; 

 a, uterus ; dm, dorso-ventral muscle fibres ; sn, suckers ; h, testes ; qm, transverse muscles ; 6ni, 

 ventral ganglionic masses ; pa, parencbyma ; md, intestine. 



The origin and places of formation of the eggs are not known with any 

 certainty. The ripe eggs pass into a spacious uterus which lies on the 

 dorsal side of the stomach -intestine. One dorsal and two lateral 

 oviduets connect the uterus with the cloaca. The male genital 

 apparatus is paired. On each side 

 branched solid testicle strands 

 lie in the parenchyma below the 

 intestine and its branchings. On 

 each side an anterior and a pos- 

 terior vas deferens collect the 

 sperm from the testes. Both 

 vasa deferentia enter a muscular 

 lateral sperm vesicle, which lies 

 between the 3d and 4th suckers, 

 and which opens outwardly at the 

 edge of the body. 



Prosopygia. — The places of 

 formation for the eggs and sperma- 

 tozoa of the Sipiinculidce, Phoron- 

 idce, and Brachiopoda are definite 

 points of the endothelium of the 

 iDody cavity. The sexual products 

 fall into the ccelomic fluid, and 

 are emptied out thence by the 



Fig. 177.— Diagrammatic representation of 



the organisation of a Braobiopofl, from tbe dor- 



nephridia, as was the case in the sal side ; the dorsal halves of shell and mantle are 



removed, ct, Arms ; mh, mantle cavity ; m, mouth ; 

 Z, liver ; mrt, stomach ; u, nephridia ; a]l, anus ; 

 cj, genital glands; I's, part of the ventral shell 

 which projects backwards over the dorsal shell ; 

 y, anterior ; 7i, posterior ; r, right ; I, left. 



Polycheeta. 



In the SipuncuUcke the formation of 

 the germs takes place for the most part 

 at the hase of the ventral proboscis 

 retractors. Phoronis is hermaphrodite. 



The male and female sexual products arise 



