PHYLUM PLATYHELMINTHES 



225 



vit 



protrusible muscular organ, the cirrus or penis (p), to open into 

 the genital cloaca. At the base of the penis, where the vasa 



differentia meet, the median 

 canal is slightly enlarged to 

 form a rounded dilatation, the 

 vesicula seminalis. 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 

 glands, uterus, and muscular sac. 

 The ovaries (ov.) 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 (lit.), 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 



kxl^J^QQy from the vitelline glands. 



f^^^ oW When the larva has reached 



>? -V a certain stage it develops a 



temporary larval mouth and 

 gullet and swallows the food- 

 Planaria. Reproductive system. J ^? ^y the aid of which it 

 m. muscular sac- ; o v. ovary ; pl< . pharynx ; PTOWS ramd 1 V Th P la TVfl 1 



p. penis; pr. prostate; tv*. testes ; ut. o " J;*r lu V' 



uterus; ,-. ,/. vas deferens ; ,-;t. vitelline mouth disappears, and a new 

 glands. (After Jijima and Hatschek.) ,-, , 



one the permanent mouth is 

 developed in its place. When 



the embryo leaves the shell it has assumed the characteristic 



shape of the parent. 

 OL. I 





