172 Retrograde Varieties 



now the presumed variety sports and runs over 

 to the presumed type, the probability of the 

 supposed relation is evidently enhanced. But 

 it is manifest that the explanation rests upon 

 the results of comparative studies, and not 

 upon direct observations of the phenomena 

 themselves. 



The nearer the relations between the two 

 types in question, the less exposed to doubt and 

 criticism are the conclusions. But the domain 

 of atavism is not restricted to the cases de- 

 scribed. Quite on the contrary the facts that 

 strike us most forcibly as being reversions are 

 those that are apt to give us an insight into the 

 systematic affinity of a higher degree. We are 

 disposed to make use of them in our attempts 

 to perfect the natural system and to remould 

 it in such a way as to become a pedigree of the 

 related groups. Such cases of atavism no 

 doubt occur, but the anomalies referred to them 

 must be interpreted merely on the ground of our 

 assumptions as to the relative places in the sys- 

 tem to be assigned to the different forms. 



Though such instances cannot be considered 

 as belonging strictly to the subject we are deal- 

 ing with, I think it may be as well to give an ex- 

 ample, especially as it affords an occasion for 

 referring to the highly important researches of 

 Heinricher on the variability and atavistic 



