Zool.-Vol. I.] RITTER—DIEMYCTYLUS TOROSUS. lO'J 



less machinelike; they crawl on the bottom part of the 

 time and swim part of the time; they vary the rate and 

 character of their movements ; they occasionally seem to 

 go somewhere in -particular , as toward a stick or stone on 

 which there is food, or toward an object under which they 

 may secrete themselves. 



It is sometimes stated concerning the larva? of other uro- 

 dela that they use their limbs as oars, but I do not believe 

 this is ever the case with these. So far as I can determine, 

 their swimming is done entirely by means of the tail. The 

 limbs are of use only in crawling on the bottom and in bal- 

 ancing themselves when suspended in the water. 



V.— THE METAMORPHOSIS. 



I have no evidence that the metamorphoses of the larva; 

 begin earlier than about the first of September, but from 

 this time on to December and January all stages of the 

 transformation may be seen in abundance, both in the 

 streams and in aquaria specimens. October appears to be 

 the culminating period of the process, since during that 

 month specimens undergoing the change, and the young 

 adults just leaving the water, are found in larger numbers 

 than at any other time. 



I am unable to say exactly how much time is required for 

 the metamorphosis. In one instance an individual showing 

 no other signs of transformation than a slight change in 

 color (see below for the order of events during metamor- 

 phosis) was taken from a stream and placed in an aquarium 

 on October 12. On the 28th of the same month the change 

 had so far advanced that the animal seemed to want to get 

 out of the water, and it was consequently transferred to a 

 moist terrarium, where it lived and flourished, though the 

 gills did not fully disappear until some days later. Obser- 

 vations noted in several other cases indicate that this is about 

 the usual time for specimens kept in the laboratory. I am, 

 however, much inclined to believe that the process goes on 

 considerably more slowly in some cases, at least in a state 



Proc. Cal. Acad. Sci., 3D Ser., Zool., Vol. I. (4) Jan. 12, 1897. 



