398 JOHN H. GEROULD 



for we have a more plausible explanation in the direct action 

 of the blood. 



If it can thus be shown that hereditary characters are directly 

 determined by the physicochemical nature of the blood, and only 

 indirectly and ab initio from the physicochemical action of 

 chromosomes, we have taken a step toward the solution of the 

 problem of the nature of mendelian factors, for the hemolymph 

 of a caterpillar, like the blood of the higher animals, is subject 

 to chemical and physical methods of analysis, and we may be 

 able ultimately to understand and control the development of 

 mendelizing and other characters that become in a new sense 

 'in the blood.' 



HOW LAMARCKIAN FACTORS MAY REACH THE GENES 



Nor should we neglect the study of the blood in its determina- 

 tive effects upon development in investigating the possibility 

 of permanent lamarckian adaptive changes. Is the blood sus- 

 ceptible to physicochemical changes due to the environment 

 that may, on the one hand, determine the course of development 

 and, on the other, produce a corresponding change in the chro- 

 mosomal enzymes, or genes, in the germ cells? If that is possible, 

 then the blood of the offspring would react like that of the parent 

 in the determination of development and a lamarckian mutation 

 would be inherited. 



It is beyond the scope of this paper to gather up and consider 

 evidence for and against this view, but the reader is asked to 

 take with some reserve Weismann's idea which since 1890 has 

 become a biological dogma that the germ cells are so isolated 

 from the soma and the world that their chromatin cannot be 

 specifically changed by environmental influences, that no mech- 

 anism exists for the transfer to the germ cells of specific environ- 

 mental effects that are observable in the soma. The blood, or 

 hemolymph, in the writer's opinion, is such a mechanism. It 

 is susceptible, especially in caterpillars, to chemical changes 

 produced by the food. Are the chromosomes of the germ cells 

 irmnune to all such changes? 



