306 GENERAL BIOLOGY 



of the systems we call specific units. In the forms 

 which reproduce sexually and they are, of course, 

 the majority of organisms the interweaving and 

 mingling of diverse genes in each generation is such 

 as to render almost futile the hope that they can 

 ever be unravelled and described. The Linnsean 

 species or phaBnotype is like a tangled and knotted 

 skein of yarn, each strand of which maintains its 

 individuality, while commingling in closest union 

 with the rest. 



THE ORIGIN OF SPECIES 



To Linnaeus and his followers, the origin of his 

 species presented no problem. They had been 

 created as such in the beginning, and had persisted 

 until the present. The relatively small number of 

 species known to him made this seem reasonable, 

 although it is likely that, had he been familiar with 

 the enormous number of forms now known, he would 

 not have been impressed otherwise than with the 

 additional evidence of the omnipotence of the Creator. 

 There is very good reason for believing, however, 

 that the doctrine of Special Creation, as it has come 

 to be called, is not tenable. Practically all modern 

 biologists believe that the species of animals and 

 plants now on the earth have not always been here 

 in their present form, but that they have become 

 transformed from other preexisting types and that 

 the constant changefulness that characterizes the 

 life of the individual is equally characteristic of 



