332 



ANIMAL BIOLOGY. 



[Part II. 



Nerve ganglia have been described in connection with the water- 

 vascular ring of the scolex. 



The scolex itself contains no reproductive organs. In the 

 metameres these organs are progressively developed, each meta- 

 mere being hermaphrodite, with cross-fertilisation. They are 



FIG. 98. TAPEWORM. 



A. Embryo with six stylets. D. Anterior metameres. 



B. Invaginated blastosphere. E. Median metameres. 



C. Scolex of bladder- worm. F. Posterior metameres. 



G. A median metamere. g. cl. Generative chamber. I. v. Longitudinal 

 water-vascular vessel, ovy. Ovary, p. s. Penis sac. r. s. Receptaculum 

 seminis. sJi. gl. Shell gland, tr. v. Transverse water-vascular vessel, is. 

 Testis. ut. Uterus, vag. Vagina, v. d. Vas deferens. vit. Vitellarium. 



H. A terminal segment in which much of the genital apparatus has atro- 

 phied, and the uterus (ut.) is distended with ova. 



seen in their most perfect condition in metameres of the stage 

 shown at E. The spermaries or testes (Fig. 98, G-., ts.) consist of a 

 great number of sperm-balls. These pour their contents into 

 efferent vessels, by which they are conveyed to the vas deferens 

 (v. d.), which opens by a protrusible termination (p. s.) into 

 a genital cloaca (g. d.\ opening into the exterior by a genital 



