158 



COMPARATIVE ANATOMY 



CHAP. 



eggs collect in these tubes, which are called egg receptacles or uterus 

 tubes (u). As they enter the female copulatory apparatus they unite in 

 an unpaired terminal portion, the egg passage, into which the thread- 

 like efferent ducts of the numerous glands (sd) which are imbedded 

 in the surrounding parenchyma open. The glands 



secretions yield the 



egg 



shell which covers the 



whose hardening 



egg 



or eggs are 



/DO 



cb 



FIG. 113. Sexual organs of a 

 Rhabdoccele (Mesostoma Ehrea- 

 bergii). To the left the testis is 

 omitted ; to the right the vitel- 

 laria and the uterus are left out. 

 h, Testis ; ds, vitellaria ; u, uterus ; 

 p, peuis ; l:s, germarium. 



FIG. 114. Sexual organs of a Tre- 

 matode (Distoma), after Leuckart. 

 A-, Testes; l:s, germarium; u, uterus; 

 ds, vitellarium ; dg, yolk or vitello- 

 duct ; vd, vasa deferentia ; Lg, Laurer's 

 canal ; cb, cirrus pouch ; mo, male, wo, 

 female sexual aperture. 



collectively known as the shell glands. They occur almost universally 

 in the Platodes. 



In the Triclada (Fig. 112) there are 2 lateral longitudinal ovi- 

 ducts (ov), which conduct the eggs from the 2 germaria in the front 

 of the body backwards to the copulatory apparatus. Apertures are 

 found on. the way, through which the vitellaria empty their products 

 into them. Before passing out into the copulatory apparatus they 

 unite to form a short unpaired egg passage, into which the efferent 

 ducts of the shell glands open. 



In the EhabdoccelidcB (Fig. 113) the female sexual glands are gener- 

 ally placed with their ends directly on the outer copulatory apparatus, 

 and open into it. There is often a union of the vitellaria and the 

 germaria before their exit into a common terminal portion. The shell 



