48 



VARIOUS FORMS OF TAPEWOKMS. 



to the intestine. There is no pr.oof yet, however, that the fox 

 does harbour this worm. It can be distinguished by having a 

 circle of hooks around its head, which is sliglitly drav/n out into 

 a rostellum, and by its four suckers. In length it varies from 

 twelve to sixteen inches when adult, and is constituted of about 

 two hundred distinct segments. The pale proglottides full of 

 eggs are passed out on to the ground in the sheep-dog's excre- 

 ment, and there remaining for a short period, they burst, re- 

 leasing thousands of ova (a). These are taken off the grass hy 



Fig. 12. — Sturdy in Sheep 

 (Ccvmirus cerebndis anil Ta'/iut canurus). 



A, Ovum. E, Embryo, o, Sexual worm (Ta'^m cffirij/j-w.^) :;., proglottides ; », neck; 

 s, suckers. r>, Gr.enuru,^ cercbrali^ : c, cerebral hemispheres; cb, cerebellum: m, 

 medulla, e, Hoolc from o. 



the lambs, or even two-year-old sheep ; sometimes even whole 

 segments may be devoured. In either case the embryos become 

 released in the stomach of the sheep. The sis-hooked larvje 

 then commence to bore their way through the walls of the ovine 

 intestine, and finally enter the blood, by which they are carried 

 to various parts of the body. Should any of these embryos 

 reach the brain or spinal cord, as very often happens, further 

 development takes place ; otherwise thoy apparently die a pre- 

 mature death. After the larva has reached the cranium, it com- 



