30 ENTOZOA. 



witliin the organs of nutrition of the living host, then they appear 

 prepared to develope themselves anew into nurse-forms ; and, 

 moreover, cercarise whose development has not yet attained a definite 

 stage — and even their tails also — appear to enjoy a similar capacity. 

 Some nurses are likewise capable of multiplication by division and 

 budding. 



" (/.) — Some germ-sacs have the property of developing within 

 themselves cercaria-like larvae — which are different from the true 

 cercarise — fi'om whose body the development of a distoma may 

 take place, while their single or double tail-like appendages in all 

 cases develop anew into germ-sacs. To this class belong Buce- 

 phalus and Distoma duplicatum. 



" (^.) — All the cercaria at present known are destitute of eyes, 

 but other forms of trematode larvae are furnished with visual 

 organs. Accordingly, 1 never found eyes in young distomata whilst 

 they were in their last dwelling-place, but eyes are certainly 

 present in the young forms of Polystoma and Amphistoma. The 

 supposition that a spontaneous wandering is associated with eyes 

 is not yet confirmed in my experience. 



" (h.) — As a means of distinguishing the different forms of 

 cercarige, among other indications, their places of dwelling may be 

 useful, because each moUusk only harbours a limited number of 

 species. Notwithstanding, Professor Filippi is in error if he beheves 

 that every species of moUusk carries only a single armed form of 

 cercaria. A migration of the cercaria is indispensable to its per- 

 fection. 



" (i.) — Many larval trematodes form cysts round themselves, 

 probably by means of a special organ of secretion, and also by the 

 epidermis. Their future. destiny necessitates this. The sporocysts 

 apparently fulfil towards the larvae which are developed within 

 them a similar purpose, namely, a protection against the 

 stomachal digestion of the new host. In the pupa condition the 

 development of the larva, which has now thrown off the tail, makes 

 greater or loss progress, according as to whether it is surrounded 



