SUMMAKY. 



77 



Sdmmaey of Platyhblminthbs and Nemathelminthbs. 



Amongst these two divisions of worms we have gone into we 

 must note several import- 

 ant points. First, their 

 parasitic habits, and the 

 often fatal results of this 

 parasitism ; secondly, the 

 almost universal rule (ex- 

 cept in many Nematodes) 

 of having two distinct 

 hosts during their life- 

 cycle ; thirdly, the ex- 

 traordhiary reproduction, 

 often asexual, and the oc- 

 casional alternation of gen- 

 erations ; fourthly, their 

 great vitality, not only in 

 the egg, but also in the 

 adult form ; and last, but 

 not least, the great part 

 water plays in their nat- 

 ural history and distribii- 

 tion. In nearly all the 

 worst forms of worms 

 producing animal diseases, 

 the worm passes some part 

 of its life in the water ; 

 for instances take the 

 Flukes, Palisade - worms. 

 Gape-worms, Ascarids, and 

 even some Cestodes. Thus 

 by paying some attention 

 to what we know of their 

 life-histories, and especi- Neumann.) 



Fig. 29.^0xyuees of Hiikse. 

 Females with long tails (-llastif/odes'). (From 



