94 CALIFORNIA ACADEMY OF SCIENCES. [3D Ser., 



about D. torosus it appears that the autumnal pairing here 

 means merely that the males lead the way by some months 

 in the yearly amours — their sexual products mature earlier 

 by this length of time than do those of the females. If we 

 might suppose that D. viridescens or its immediate ancestors 

 once lived in a climate something like that now prevailing in 

 California, where the winters were not sufficiently rigorous 

 to materially retard their physiological processes, we might 

 then suppose that its autumnal mating was likewise the lead- 

 ing of the way by some months of the males in the sexual 

 activity of the year. Then with a change in climatic con- 

 ditions, either by a migration of the species or by an actual 

 change of climate, the severe cold of winter intervened be- 

 tween the time when the males began their amours and 

 that at which the females were ready to co-operate with 

 them in the reproductive act. Still, from old habit the males 

 began their amorous advances as before ; but by the severity 

 of the cold to which they later became subject, they suffered 

 a check in their activities till warmth returned with the fol- 

 lowing spring; and such an order of procedure as we now 

 see in the species resulted. But in this connection it is im- 

 portant to bear in mind that in some species of urodelos 

 Amphibians, i. e., Salamandra maculosa, KnauerC^S) and 

 Pfitzner ('80), the same females reproduce regularly twice 

 a year, in spring and in autumn. 



That internal fertilization occurs in this species, as has 

 now been amply proved to be the case in numerous other 

 Urodela, there can be no doubt, since females kept in the 

 laboratory isolated from the males have frequently deposited 

 eggs, and these have always developed in all respects like 

 those deposited under natural conditions in the streams and 

 ponds. Unfortunately my observations on this point are 

 incomplete. The animals appear adverse to carrying on 

 their amours in captivity; at least they have thus far not 

 gratified my desire to have them do so. My information is 

 consequently limited to what I have seen them doing in 

 their natural haunts. 



While, therefore, I have not been able to determine with 



