PIGMENT CHANGES IN ANURAN LARVAE 121 



ing the course of the experiments, Elodea and other aquatic plants 

 were used as the source of food supply. Before operating, the 

 animals were anaesthetized in a weak solution of chloretone, 

 and after all movement had ceased were transferred to wet towel 

 paper, ventral side up. A small transverse slit through the body- 

 wall and peritoneum was made wdth dissecting scissors, just lateral 

 to the median line above the mesonephros. The glandular tissue to 

 be transplanted was then shoved through the opening with a blunt 

 needle back toward the median line of the body. In many cases 

 the tissue was transplanted in the abdominal lymph sacs. Either 

 method is satisfactory and equally simple. The mortality re- 

 sulting from such operative procedure is practically negligible. 

 It is a rather striking fact that an operation as severe as an incis- 

 ion into the body cavity should be followed by such rapid recov- 

 ery and so few fatalities. There is, however, practically no loss of 

 blood, and the wound is very soon closed by a lymph clot 

 that serves to hold the transplanted tissue in place and prevents 

 other foreign substances from entering the body cavity. Recov- 

 ery from the effects of the chloretone is rapid, and apparently no 

 part of the procedure causes any harmful results. Normal ani- 

 mals used as check controls were treated in a similar way with 

 engrafted brain and muscle tissue instead of glandular substance. 



The glandular material was taken from adult frogs of three 

 species, Rana catesbeiana, Rana pipiens, and Rana clamitans, 

 several young specimens of the latter species were also employed. 



The hypophysis of an adult frog is readily dissected out by 

 first severing the head from the body just behind the medulla, 

 and then with a pair of sharp-pointed dissecting scissors clipping 

 away the floor of the brain case and exposing the gland. I have 

 found it expedient to cut out the hypophysis and tuber cinereum 

 as a unit in my later experiments, on account of the intimate 

 relation between the pars tuberalis of the hypophysis and this 

 portion of the brain floor. 



It is well known to ail recent investigators of the pituitary 

 that the gland consists of four parts or lobes, as they are sometimes 

 called, each portion distinct from the others both ontogeneti- 

 cally and histologically. The epithehal part of the pituitary 



