HORMONE FACTORS IN GROWTH AND DEVELOPMENT 191 



constantly a precocious commencement and an increased rate of crowing in 

 anterior lobe-fed male birds. Clark claimed that anterior lobe feeding 

 stimulates the egg laying in hens, but this assertion was disproved by 

 Pearl and recently by Simpson. 



O Q 



\ 



Fig. 2. Two female Ambystoma opacum; A an anterior lobe-fed, B a control 

 animal. A (130 mm.) is the largest hypophysis-fed animal, B is one of the largest 

 animals reared in our laboratory 4 (the largest animal reared in the laboratory was 

 113 mm., the largest animal among those caught in nature or found in museums 

 was 117 mm. long). Reduced. Original. 



Relations in Mammals. Although numerous experiments were car- 

 ried out on mammals, the results in this group of organisms are often con- 

 tradictory and unreliable on account of the lack of proper controls and an 

 insufficient number of experiments. Despite many negative experiments 

 it seems, however, safe to say that also in mammals feeding of anterior 

 lobe results in an increased rate of growth, and in precocious development, 

 especially of the sex glands and secondary sex characters. Although ex- 



