Zool.— Vol. I.] HITTER— DIEMYCTYLUS TOROSUS. 87 



usually arrive at sexual maturity when three years old. 

 Sexual maturity in the males is not reached, so far as I 

 know, until the aquatic habit is assumed for the second 

 time, and the tail has again become much expanded and 

 laterally compressed. A change of color is, however, not 

 essential to the arrival at this state. We are not, therefore, 

 it appears to me, justified in speaking of a second trans- 

 formation in this species as Gage does in D. viridescens. 

 The difference between a young adult male and a sexually 

 mature one is certainly considerable, but it is very much less 

 than that between the gill-breathing larva and the adult. Fur- 

 thermore, the transition to the mature condition is much more 

 gradual than is the true metamorphosis. But what is most 

 important of all, and what constitutes the greatest distinction 

 between the two species, is the fact that, according to Gage, 

 the viridescent, or adult form of the eastern species, having 

 been once assumed, the red form is never again reverted to; 

 our species, on the other hand, may certainly go back from 

 the condition which seems to correspond to the viridescent, 

 or adult form of the eastern species, to that which apparent- 

 ly corresponds to the red, or immature adult stage of that 

 species. The characteristics of the two conditions in our 

 species will be readily understood by an examination of 

 figs. 1, 2 and 3. 



Figure 3 represents a full-grown male, as these are 

 frequently found in autumn, crawling about on land, quite 

 remote from any water. 



Figure 2 represents another of about the same size, 

 taken from the reservoir at North Berkeley, on the first of 

 January, 1896; i. e., during the height of the season's 

 amours. (I point out elsewhere that the males lead the 

 way by some weeks in love-making, so that egg-laying does 

 not begin for some time after the males are abundantly pre- 

 pared for the occasion.) 



In addition to the great width of tail and strength of limbs 

 of the latter as compared with the former, which conditions 

 come out with ample distinctness in the figures, there is in 

 reality a difference almost as striking and characteristic in 



