RESULTS OF CASTRATION 51 



that Goodale has recorded a fact which at first sight is not 

 conformable with the theory of an asexual embryonic soma. 

 He found that in some cases the castrated duck not only 

 assumed the ordinary male plumage but at moulting time 

 changed it for the male summer plumage. We shall discuss 

 in Chapter IX. what factors could have been at work here. 



D. THE RESULTS OF CASTRATION IN THE FROG 

 AND IN FISHES. 



We have already referred to the relations existing between 

 the sexual glands and the phenomena of heat or oestrus. 

 These relations have been studied with full particulars in the 

 irog, and by the investigations of Nussbaum, Steinach, Meisen- 

 heimer and Harms results of a general interest have been 

 obtained. In the spring, at the time of copulation, quite 

 •characteristic morphological and functional changes take 

 place in the male and female frog. In the male the pad on the 

 skin of the first digit of the fore limb enlarges. The pad is 

 histologically characterized b}^ a thickening of the epidermal 

 •epithelium, by an augmentation of the glandular tissue, and 

 by an accumulation of pigment (see especially Harms^ ^9M> 

 ^pp. 230-231) {Figs. 35 and 36). Also the muscles of the fore 

 arm hypertrophy {Nussbaum, 1912). Amongst the changes in 

 the sexual organs the increase of the vesiculae seminales 

 must be mentioned. Functional signs of the oestrus are the 

 <:haracteristic sound of the male and the clasping movement 

 or reflex. This reflex of the male in heat is highly developed; 

 in the breeding season males may be often found embracing 

 dead fishes or pieces of wood. The clasping movement can 

 be evoked at once when the skin of the chest is touched by 

 the finger. The male presses the tuberculate pads on to the 

 chest of the female, and the skin of the latter will be often 

 found rubbed through to the muscles. 



All the above-mentioned characteristic signs of the oestrus 

 fail to develop if the animal has been castrated some time or 

 other after the last oestrus. The vesiculae seminales remain 

 -small, the pad does not develop to the normal size, and the 

 clasping reflex does not develop to the normal degree 

 {Nussbaum, 1909, pp. 530, 532, 534; M eisenheimer , 1912). 

 Steinach (1894, pp. 313, 314) castrated a number of specimens 



