THE GENETIC AND THE OPERATIVE EVIDENCE 



directly on some specific part of the body or whether in doing so it 

 acts on other parts as well. While it is more or less customary to 

 limit the term " hormone" to substances that do produce specific 

 effects in a particular organ, no one would, I suppose, deny that 

 a substance was acting as a hormone if at the same time it acted on 

 other parts of the body also, or even if its immediate action were on 

 some part and its ultimate action on another part of the animal. 

 Moreover, there is nothing in the evidence appealed to by Smith that 

 supports one rather than the other contention. It is not apparent that 

 the simpler idea of hormone action may not still apply. Failure to 

 implant the testes in castrated male or female, and failure of injections 

 to produce the results sought for, may mean no more than that the 

 experimenter failed to fulfill some one of the conditions present in the 

 normal frog at the breeding-season. Granting that the results recorded 

 by Nussbaum and Meisenheimer are open to the serious objections, 

 pointed out by Smith and Schuster, the facts recorded by all three 

 writers indicate that the maximum development of the pad takes 

 place when the testes are at their greatest development and that the 

 pad suddenly decreases if at this time the testes are removed. It 

 would seem to follow that since the swelling is connected with the 

 presence of a certain condition of the testes, its enlargement is to be 

 referred directly to the latter, and the case comes under the general 

 category of " secondary sexual differences," depending on the gonad. 



The secondary sexual characters of Triton cristatus can not, as can 

 those of the frog, be supposed to be mechanically useful in mating, but 

 seem to be comparable in every respect with the secondary sexual 

 ornaments of higher animals. The work of Bresca has shown that their 

 development is under the influence of the testes. The most important 

 secondary sexual characters of the male are the dorsal comb and the 

 white stripes of the tail. The comb extends along the dorsal surface 

 of the body and of the tail (with a slight dip in the pelvic region). It 

 is fully developed during the breeding-season, when it reaches a height 

 of 1.5 cm. In winter it is only 0.66 mm. high, or even less. The white 

 stripes also are fully developed in the breeding-season. They extend 

 on each side from the cloaca to the end of the tail. In the female the 

 white stripe is sometimes faintly seen. The angles of the tail and of the 

 cloaca thickening are black-brown or black. The belly of the male is 

 bright orange or "Ziegel rot"; that of the female sulphur-yellow or 

 orange, but the difference is not constant. The upper surface of the 

 head of the male is marbled, especially during the breeding-season 

 almost disappearing during the rest of the year. Bresca found, when 

 the testes were removed from sexually mature males, that in the course 

 of a year all the important secondary sexual characters disappeared, 

 including the comb, the white tail stripes, and the marbling of the 

 upper surface. Removal of the ovaries did not affect the characters of 



