PART XII 



MONSTROSITIES AS PROBABLE FACTORS IN THE 

 CREATION OF SPECIES 



THE study of monstrous forms, both in the vegetable and animal 

 worlds, is very interesting, because, not infrequently, some important 

 secrets of nature are thereby revealed, which no one would suspect 

 from the contemplation of simple normal forms. This study of 

 monstrosities has been dignified by the euphonious term of 

 Teratology, and elevated into a branch of the science of biology : 

 but I do not yet see that monstrous forms have taken their place 

 as links in the method of creation by evolution. 



What is a monstrosity ? Darwin says 1 ' By a monstrosity I 

 presume is meant some considerable deviation of structure 

 generally injurious, or not useful to the species.' 



And on p. 52, he says 'Under domestication monstrosities 

 sometimes occur which resemble normal structures in widely 

 different animals. If monstrous forms of this kind ever do appear 

 in a state of nature, and are capable of reproduction (which is not 

 always the case), as they occur rarely and singly, 2 their preservation 

 would depend on unusually favourable circumstances. They would 

 also during the first and succeeding generations cross with the 



1 Origin of Species, vol. i. p. 51. 



2 We have absolutely no means of knowing that in ancient times they did not occur 

 in numbers. 



