PHYLUM PLATYHELMINTHES 



protrusible muscular organ, the r 

 the genital cloaca, At the base 



i 'if 



Flo. 173. Planaria. Reproductive system. 

 in. muscular sac ; or. ovary ; ;i/<. pharynx ; 

 j>. penis ; pi-, prostate ; tes. testes ; ul. 

 uterus ; c. it. vas deferens ; fit. \-itelline 

 glands. (After Jijima and Hatschek.) 



the embryo leaves the shell it 

 shape of the parent. 

 VOL. I 



i mis or penis (p), to open into 

 of the penis, where the vasa 

 differentia meet, the median 

 canal is slightly enlarged to 

 form a rounded dilatation, the 

 Tcsicuia seminahs. Into the 

 median canal open the narrow 

 ducts of a number of unicellu- 

 lar glands, the prostate glands 

 (pr\ 



The female part of the re- 

 productive apparatus consists 

 of ovaries, oviducts, vitelline 

 !/lands, uterus, and muscular sac. 

 The ovaries (or.) are two in 

 number small rounded bodies 

 situated near the anterior end, 

 each connected with an elong- 

 ated duct, the oviduct. The 

 two oviducts (od.) unite pos- 

 teriorly to form a short median 

 common oviduct opening into 

 the genital cloaca. With this 

 cavity are connected also the 

 uterus (ut.}, a median rounded 

 chamber, and a thick-walled 

 muscular body, the muscular 

 sac (m.). Numerous branching- 

 tubes the vitelline glands (vit.} 

 open into the oviducts. 



Reproduction is entirely 

 sexual. The oosperm is en- 

 closed within a protecting case 

 or shell, which contains also 

 a quantity of food-yolk derived 

 from the vitelline glands. 

 When the larva has reached 

 a certain stage it develops a 

 temporary larval mouth and 

 gullet and swallows the food- 



tolk, by the aid of which it 

 rows rapidly. The larval 

 mouth disappears, and a new 

 one the permanent mouth is 

 developed in its place. When 

 has assumed the characteristic 



Q 



