358 WILLIAM H. COLE 



decaying animal matter, were offered without success. The ac- 

 tual food supply seemed to come from the algae, plants and mud 

 in the jars. The absence of the vigorous feeding reactions shown 

 by young tadpoles in the spring and summer was very marked. 

 It was concluded that frog tadpoles of these species must have 

 a lowered rate of metabolism during the winter months. In 

 their natural habitat, no doubt, such a lowered metabolic rate 

 occurs, due partly to the continued low temperature of the water. 

 However, aside from this, the animals appeared normal in every 

 way and responded to the usual stimuli. Many of them were 

 kept in the small jars seven and eight months, a few of them 

 undergoing metamorphosis. Except in some of the experiments 

 to be noted later, the jars were kept on a table in diffuse daylight. 

 The method of procedure in transplanting integument was as 

 follows. The animals were placed in 0.1 per cent aqueous solu- 

 tion of chloretone (trichlortertiarybutyl alcohol; Parke, Davis 

 <fe Co.), which anaesthetized them sufficiently for the operation 

 in from six to fifteen minutes. The minimal time for anaestheti- 

 zation is determined principally by two factors: size of the ani- 

 mal and the temperature of the solution. As the temperature 

 increases, the time decreases; but as the size of the animal in- 

 creases, the time increases. A square or other rectangular 

 incision with a perimeter of about 24 mm., was made in the integ- 

 ument where the transplant was to be placed. In some cases 

 all of the integument within the incision was removed; in others 

 the integument was left within the incision. When the graft 

 was placed over the eye, the conjunctiva lay within the incision, 

 as shown in text figure A. The transplant consisted of integu- 

 ment taken from one of three different regions of the same animal 

 (autotransplantations), or from a different animal not closely 

 related (homoiotransplantations) . The three regions were: pos- 

 terior part of the tail, middle of the back, and middle of the belly. 

 In every case it was cut so as to fit as nearly as possible the inci- 

 sion to which it was transplanted. The grafts taken from the 

 tail consisted of one-half the thickness of that structure, con- 

 taining integument, the muscle layer and the notochord. Since 

 the transplant was taken from near the base of the caudal fin. 



