76 CALIFORNIA ACADEMY OF SCIENCES. [ 3 d Ser., 



can only say that I am unable to detect such a distinction. 

 In fact, the reverse is more nearly true; i. e., the toes of 

 " Icevis " are, in proportion to their thickness, less elongated. 

 The most complete and accurate description that we 

 have of the species, particularly of its seasonal varia- 

 tions, is by Cope ('89). To this author's work I shall refer 

 several times later on. Brief references, unimportant from 

 any but a classificatory point of view, have been made to 

 the species by Baird ('47— '50), Skilton, and Boulenger 

 ('82). 



II.— The Adult. 



General. — It would be superfluous to give here a gen- 

 eral description of the animal, since those by Eschscholtz, and 

 by Girard, and particularly that by Cope, are quite adequate, 

 and the last mentioned is readily accessible to most zool- 

 ogists. As concerns the adults, therefore, I have only to 

 deal with those special points, knowledge relating to which 

 could be obtained only by continuous observation of the 

 animals, living and dead, in large numbers, both in con- 

 finement and in their native haunts, and at all seasons of 

 the year. 



I do not use the term adult as meaning full-grown, but I 

 speak of the animal as adult as soon as its metamorphosis 

 is complete. Gage ('91) applies the word only to the olive- 

 green, or viridescent form of Diemyctylus viridescens; but 

 since there does not exist, as we shall see later, so trenchant 

 a division of the life of our species into two periods as is 

 the case in D. viridescens, and since I do not know defi- 

 nitely about the limit of the period of growth, I see no 

 satisfactory way of using the term here excepting that in- 

 dicated. How long the animal lives, whether or not it 

 grows during its whole life, and at what age it becomes 

 sexually mature, are questions which I am as yet able to 

 answer only partially. 



The average length of nine specimens just metamorphosed 

 I found to be 48 mm. The largest one of this age that I 



