Zool— Vol. I.] RITTER—D1EMYCTYLUSTOROSUS. Ill 



the same kind of an aquarium as to size, shape, relation to 

 light and temperature, quantity and quality of water and of 

 food, as were all the others that underwent metamorphosis 

 in the fall and early winter of last year. If the different re- 

 sults are due to difference in conditions, the differences 

 have been so slight that nothing short of the most exact 

 measurements and observations would detect them. Some- 

 time in the future I hope to subject the matter to rigorous 

 experimentation ; but for the present I merely point out 

 that such a course is essential in order that we may know 

 the conditions under which one of the three following fun- 

 damental but obviously possible things will happen in the 

 lives of these larva?: (i) When they will develop into 

 normal adults; i. e., adults capable of perpetuating their 

 kind; (2) when they will remain in the larval condition; 

 i. e., in a condition such that were it to be retained by all 

 the individuals hatched for a few consecutive years the ex- 

 termination of the species would be the result; or (3) when 

 they will reach reproductive maturity in the larval state, 

 thus originating a possible new species, or even a new genus, 

 of Urodela. Were sexually mature larva? of this species to 

 continue to live and reproduce in this condition throughout 

 their lives, generation after generation, even if this were 

 demonstrably dependent on external conditions, I suppose 

 most zoologists would no longer regard them as Diemycty- 

 lus torosus larvae, but would look upon them as a new 

 species. 



With the completion of the metamorphosis, the adult state, 

 in the sense in which I have used the term, is reached, and 

 since our account began with this stage in the animal's life 

 history, we have now returned to our starting point. 



