112 Journal of Comparative Neurology. 



May of this year. In dealing with the spring frogs as contrasted 

 with those taken later in the season, we had occasion to observe 

 a peculiarity not previously noted. Our custom was to get a 

 dozen frogs, freshly caught, and work them over at the rate of a 

 frog each day. The relation between weight of the body and 

 that of the central nervous system soon indicated that during 

 their stay in the laboratory the frogs in question were losing 

 rapidly in their body weight, the weight of the central ner- 

 vous system remaining, so far as we could determine, quite 

 unaltered. 



Acting on previous experience with Bull-frogs as to the 

 manner in which frogs gain and lose water, the specimens to 

 be examined were at this time always kept in tanks containing 

 a few stones surrounded by shallow water, and previous exper- 

 ience with summer frogs had indicated that little or no change 

 in body weight would occur under these circumstances during 

 a period of one or two weeks. 



Under these same conditions however, the spri?ig frogs 

 lose weight very rapidly. The following experiment will illus- 

 trate this point : 



Four specimens of R. virescens brachycephala were weigh- 

 ed separately and numbered. They were kept in the dark in a 

 tank through which water slowly flowed, and were weighed for 

 twelve consecutive days at intervals of twenty-four hours. The 

 records of the body weight at intervals of four days are given 



below. 



TABLE I. 



Showing loss of weight in spring frogs kept under favorable conditions in 

 the laboratory. 

 No. of Frog. I II III IV 



On the morning of May 15th., a tragedy occurred. Frog 

 No. I swallowed frog No. IV and thus closed this set of obser- 

 vations. There are a number of interesting changes brought out 

 by an experiment of this sort, but we pass them here as irrele- 

 vant to our present purpose. 



