54 INTERNAL SECRETIONS 



pads, though microscopically easily visible, is not to be com- 

 pared to that observed in the normal animal during oestrus. 



Speaking generally then, we see that in amphibians the 

 development and the maintenance of oestrus depend on the 

 sexual gland. Though the cyclical changes take place to a 

 certain degree after castration, whether carried out before or 

 during the oestrus, a normal oestrus will never recur. According 

 to Kammerer (19 19, p. 341) it is not the same with the male of 

 Alytes, in which a pad on the fore limb was produced under 

 conditions of experimental breeding. When Kammerer forced 

 the frog to spawn in the water, the males of the next genera- 

 tion got pads. If male Alytes bred in that way are castrated, 

 the oestral pad reappears nevertheless at every oestral season. 

 Kammerer concludes from his experiments that in Alytes the 

 regeneration of the pad does not depend on the sexual gland. 

 But I think that the question of the inheritance of acquired 

 characters is such a complicated one that it would be unwise 

 to draw from Kammerer' s experiments any definite conclusions 

 concerning the dependence or independence of oestral changes 

 in relation to the sexual glands in amphibians. 



If we compare these data upon the dependence of the oestral 

 phenomena on the sexual glands in Amphibia with what we 

 learned as to the significance of the sexual glands in relation to 

 the development and the preservation of the sexual characters 

 in man, mammals and birds, we find a parallelism in the 

 behaviour of the different species. In some cases the sexual 

 characters are dependent on the sexual glands, but in others 

 the sexual characters may continue to exist or even develop 

 further after castration. Also one might suppose that these 

 apparently independent sexual characters — the c^^clicaUy 

 reappearing weakened embracing-reflex, the formation of the 

 pad — were already established by the formative function of the 

 sexual glands at the time when the castration was done. 



Observations on fishes have been made by Koped (19 18). 

 He castrated the common fish Phoxinus laevis, which exhibits 

 in the spring a red nuptial colouring in the back, both 

 in the male and female. The animals survived the operation 

 only for three weeks, but results of castration were obvious. 

 In two series of experiments out of 30 animals castrated in 

 April and March only 7 exhibited the nuptial colour, whereas 

 out of 18 partially castrated animals (half a testicle on each side 



