I0 o VARIATION 



Derangements of a more fundamental nature often arise dur- 

 ing embryonic development, resulting in monsters of all degrees 

 of abnormality. Teratology has little interest to the biologist 

 generally, because these abnormal caricatures of life constitute 

 nothing but sporadic offshoots of the species. Developing 

 from defective germs and having no connection with the line of 

 descent, they are of little interest to the evolutionist. Their 

 interest to the thremmatologist lies in their bearing upon func- 

 tional activity and the degree of certainty with which specialized 

 tissues may be depended upon to discharge their hereditary and 

 proper functions. 



Variation due to the suppression or failure of the reproductive 

 functions. The abdomen of the crab Carcinus mcznas normally 

 has seven segments. In the female these are distinct. In the 

 male the abdomen is much narrower, and the divisions between 

 the third, fourth, and fifth segments are obliterated. Males, 

 however, inhabited by the parasite Sacculina do not develop 

 sexual characters, and in them the segmentation is complete, as 

 in the female.? 



A young male is castrated. The parts removed are in no 

 sense vital, and they seemingly have no connection with other 

 organs of the body. All the bodily functions except those of 

 reproduction proceed, but not as before. In general the develop- 

 ment of the shoulders and neck will be arrested, and they will 

 remain lighter and finer. The voice, the nervous temperament, 

 the disposition, and the general activity of the body are all 

 affected. The mane of horses will be thinner, finer, and shorter. 

 The hair of face and neck in cattle will be finer and less curly. 

 In hogs the tusks and shoulder plates do not develop. The growth 

 of the horns is lessened in sheep, but in cattle the only effect is 

 to make them slightly longer and a little more slender, ap- 

 proaching the female type. The hinder parts of the body as a 

 whole develop rather more in castrated than in entire animals, 

 and there is a general approach to the form of the- female. It 

 is noteworthy in this connection that the same general effect 

 follows the failure of the sexual powers with advancing age, 

 except that the body development has already taken place. 



1 Bateson, Materials, etc., p. 95. 



