110 THE AMERICAN MONTHLY [May, 



relationship or kinship between animals presenting them. Thus the 

 i-ed and grey squirrels by the Agassizian school resemble each other 

 more than either does the gopher, merely because they were made by 

 their maker as modification of one plan in his mind, while their resem- 

 blance appears to the other school to indicate a comparatively close 

 actual kinship. 



The latter conception is the Darwinian view ; it extends the operation 

 of descent, which is a natural phenomenon, never having been called in 

 question by any thinkers so long as its operation is confined to the rela- 

 tionship in one '^ species," to the entire range of animals and plants. 

 The Darwinian view of the meaning of classification, then, is that resem- 

 blances between living things really indicate, as they seem to, a kinship. 

 Heredity is thus a conservative factor if its range is thus extended and 

 tends to keep animals alike down to very remote generations. Heredity 

 may then accoimt for the likeness among animals widely remote in their 

 relationship, as, for instance, fishes, reptiles, birds, and mammals, but, as 

 ^ye have considered it thus tar, will it account for their difterences.^ 

 We may note in the third place that the difterences between animals 

 might conceivably be due to the interaction between the inherent and 

 hereditary tendency and the environment of the animal. The French 

 zoologist Lamark was acute enough to think of this, and he proposed 

 to explain the order of the animal and plant worlds upon the two as- 

 siunptions that the use of organs modifies their structure, and that parents 

 transmit this modification of structure as well as their general race type 

 of structure. His theory attracted but little attention at the time. Un- 

 fortunately for Lamark's theory there are very few facts which go to 

 prove that modifications of structure acquired during the lifetime of an 

 individual can be transmitted by heredity. Modifications of structure 

 which appear " congenitally," as it is termed, that is, those which are, 

 so to speak, born in an individual so that they are independent of the 

 . animal's environment, are well known to be transmissible. Thus, for 

 example, a cat born tail-less or six-toed would be likely to transmit the 

 peculiarity to its offspring, but one who had lost a tail or gained a toe 

 by accident during adult life would be almost certain not to transmit 

 the peculiarity. Lamark's 2:)roposition is therefore not obviously true 

 to facts. 



Before going further, I may now call attention to the importance for 

 clearness of distinguishing modifications of structure which have been 

 the direct result of the use of organs called acquired characters and 

 modifications which have appeared in an individual independently of 

 use, such as monstrosities for instance, or sports among plants, as well 

 as hundreds of slight and hence unnoticed ones which are called " con- 

 genital variations." Heredity is admitted by about all writers to include 

 the parental type and any congenital variations. 



Darwin, in his theory of organic evolution, sought to account for the 

 varied forms of animals and plants as the outcome of transmission of race 

 type and congenital variations with the supplementary effect of crowd- 

 ing, which would cause a natural selection of the best for breeding, the 

 poorest having succumbed in the contest for life. This theory left too 

 much to the element of chance in accounting for the appearance of fav- 

 orable congenital variations at the critical time, and Prof. E. D. Cope, 

 whose studies had been chiefly among the osteological features of verte-. 



