EXTIRPATION OF ANTERIOR LOBE OF HYPOPHYSIS. 



119 



seeing and removing it. In each case it was broken away from 

 the ectoderm to w r hich it was still attached at the stage at which 

 the operation was performed. In most instances the dorsal 

 portion of the pharynx was partly removed ; but, as will be seen 

 later, this did not appear to affect the formation of the thymus 

 glands. 



The tadpoles recovered very quickly from the operation, heal- 

 ing of the wound taking place in the course of 20 or 30 minutes, 

 after which the tadpoles became as active as ever and appeared 

 to be quite normal. In about 1/3 of the cases the anlage of the 

 upper part of the mouth was so injured by the operation that it 

 developed imperfectly, hence these individuals were doomed to 

 starve. Observations upon this point were made in the following 

 lots as indicated : 



The operated tadpoles grew quite normally resembling the 

 controls in every regard until 7 or 8 days after the operation 

 when they were 8 mm. in length. They then underwent a 

 striking color change from the earlier solid black to a bright 

 creamy silver color, becoming really quite handsome creatures. 

 In the controls many pigment cells are found in the lower layer 

 of the epidermis, where they give off a rich network of processes. 

 In sharp contrast to this is the fact that in the tadpoles deprived 

 of the hypophysis only very seldom can a much contracted pig- 

 ment cell be demonstrated in the epidermis. It seems quite 

 certain that the pigment cells have migrated to deeper positions. 

 In both the controls and the operated tadpoles they are found in 

 great numbers on the surface of the skull, the inner surface of 

 the gill cavity, the outer surface of the heart, within the brain, 

 and spinal cord, upon the gills, in the pericardium, very ex- 

 tensively in the peritoneum, in the pronephros, liver, thyroid, 

 lungs, intestine and walls of the blood vessels, but there is a 

 constant difference in that they are expanded in the normal 



