228 CASES SIMULATING ALTERNATION OF GENERATIONS. 



consistent with precision of language, as well as with the 

 true theory of development. A medusoid, for instance, 

 is something more than an egg-sac or egg-carrier, it is an 

 egg-producer, and the precursory form of a Trematode is 

 neither one nor other — it is indeed a producer of its brood, 

 not a mere carrier, but the brood consists neither of eggs, 

 nor of embryos produced from eggs, but of zooids formed 

 by a fresh act of gemmation. 



Such objections are perhaps hypercritical, but the im- 

 portance can hardly be over-rated, in a perplexed subject 

 like the present, of avoiding the use of expressions which 

 may in any way become a fresh source of confusion. 



