88 The Mechanism of Evolution in Leptinotarsa 



Of the somatic determiners I have found only three thus far, although further 

 study may no doubt show more. Corresponding to each of the basal factors 

 there are in some instances two chromatic receptors, each with its determiners. 

 For three of these basal factors two chromatic receptors have been identified, 

 each with one or more determining agents, and for the remaining six, one 

 chromatic receptor with its determiners. The chromatic determiners are 

 numerous, about 50 such major agents having been found, many of which are 

 obviously compounded of many minor agents, or at least are capable of frag- 

 mentation and extensive modification through diflferent processes. 



It is perhaps suggestive, certainly not conclusive, that the number of basal 

 factors, 9, corresponds with the reduced number of chromosomes in the gamete, 

 and that for some of these there are two groups of chromatic agents, which, if it 

 is true for all the basal factors, would give 18 such groups, which is the 2X 

 number of chromosomes in the zygote, so that there is possibly some real rela- 

 tion between these findings ; in fact, I am at present inclined to the hypothesis 

 that there is a rather specific relation. 



It seems to me that the best interpretation of the findings is that the com- 

 monly dissociated and interchanged agents are, as Morgan shows in Drosophila, 

 probably located upon the chromosomes. The apparent number of basal factors 

 in Leptinotarsa, 9 (with the two pairs of interacting groups of agents for three 

 of them) suggests, but by no means proves, rather important relations that 

 further investigation may make certain. In tables 2 and 3 I have given a list 

 of the different agents and the symbols used in their description in the follow- 

 ing pages : 



I picture the gametic material, then, as a mixture of substances, each more 

 or less independent and concerned in special manifestations of the whole, result- 

 ing through the numberless interactions in the correlation of form and activi- 

 ties, qualities, and attributes in local and general characters, producing the 

 total array that we know. In many aspects it appears to me not unlike many 

 another terrestrial stratum — a mixture of different materials, yet presenting 

 generic characteristics and endless minor specific differences. Granites, com- 

 pounded of certain substances, all have generic likenesses of form and structure ; 

 but with the differences in proportion of the factors of composition, with the 

 varying action of the conditions of the medium at the time of combination, or 

 by the press of conditions after the original production, produces granites of 

 many kinds. May it not be profitable for a time at least to view organisms in 

 much the same manner as a product integrated in the contact zone between the 

 atmosphere and lithosphere as purely physical and mechanistic productions of 

 the geological and cosmic forces incident upon the planet's surface? At the 

 least I have tried to show the standpoint from which I must approach the prob- 

 lems and the concept held of the nature of the gametic material or germ-plasm, 

 which is the basis of organic evolution and activity. I can not but feel that in 

 the intensity of modern life and its necessary specialization we have become 

 too intensely biologists, too little natural philosophers; that in the specializa- 

 tion, so characteristic of our period, there is unfortunate liability to lose sight 

 of broader relations and points of view, and in the restriction of activities to 

 narrower and narrower fields unintentional error and misconception unwit- 

 tingly creeps in. The naturalistic point of view is true in part, it must be in all. 



