366 ON POLYCERCUS, 



Numerous attempts were made to develop the adult tape-worm 

 by feeding cats, a bandicoot, pigeons, gulls, fowls, and lizards with 

 the cysts ; but no Ttenia was found that could be assigned to the 

 species under investigation. 



The infested earthworms (PI. xix. fig, 1) usually contain immense 

 numbers of cysts, the largest of which are about a millimetre in 

 diameter, adhering in clusters to the outer surface of the alimen- 

 tary canal. Each cyst (fig. 2) contains in its interior a number — 

 usually eight to twelve, sometimes as many as thirty — of fully- 

 formed Cysticercoids, with, sometimes, a few in early stages of 

 development. In many cases the cavity of the cyst in the 

 interstices between the Cysticercoids is filled with blood, showing 

 that the cyst has been formed rather in the wall of the dorsal 

 blood-vessel or one of its main branches than in the wall of 

 the alimentary canal, and that there has been a communication 

 (afterwards sometimes found to be persistent and distinguishable 

 in sections) between the lumen of the vessel and the cavity of the 

 cyst. A few cysts w^ere found which contained only the earlier 

 stages and no fully developed Cysticercoids. Nothing was seen 

 of hooked embryos. 



In the earliest stage observed the cyst contained a solid 

 spheroidal mass of soft small-celled tissue, which was not connected 

 in any way with the cyst- wall. The latter was mainly, if not 

 entirely, of the character of an adventitious cyst : if any part of 

 it had been developed from the hooked embryo, it was no longer 

 distinguishable. In the next stage the mass had lost its former 

 spheroidal form owing to its having become'drawn out into several 

 lobes. The lobed mass then develops a number of buds. These 

 are at first very small blunt processes (fig. 3). Gradually they 

 become larger (figs. 4 and 5) and assume a rounded shape, broader 

 distally than proximally, where there is a slight constriction. As 

 they increase in size they assume an oval form and become con- 

 stricted off from the parent mass, remaining attached to it only 

 by an isthmus or stalk (fig. 6), which in the largest becomes very 

 narrow. Up to this point the bud has consisted of a nearly 



