GENERAL DISCUSSION. 



I shall undertake no real general discussion of the problems of 

 inheritance : not even of those particular ones upon which this silkworm 

 work may have some bearing. The few points to which I shall here 

 briefly call the reader's attention will be chiefly simply by way of indi- 

 cating or drawing certain comparisons with the conclusions of Toyama 

 (Bull. Coll. Agric., Tokyo Imp. Univ. v. 7, pp. 259-391, 1906) based 

 on his similar work with silkworms, and with those of Davenport 

 (Paper No. 7 of the Carnegie Station for Experimental Evolution, 

 1906) based on his work with poultry. 



Toyama finds the larval variations of color-pattern and the cocoon 

 differences of color to follow Mendel's law, and to behave with equal 

 consistency and regularity. I do not. By the use of many repetition 

 or check lots I find the larval characters to exhibit a great fidelity to 

 Mendelian principles in their mode of inheritance, but with the cocoon 

 colors I find exceptions so numerous, so various, and so pronounced as 

 to lead me to lay great stress on the potency or influence of individual 

 and strain idiosyncrasies. My position in this matter has been already 

 definitely set out in this paper in the sub-section "Conclusions" of the 

 section "Strain and Individual Idiosyncrasies" (p. 33). 



I have stated there what seems to me to be the probable significance 

 of the facts of this marked difference in the consistency of the inheri- 

 tance behavior of these two sets of characters. This significance is, 

 in a word, that the regularity and consistency of the behavior of the 

 larval characters result from their natural origin and fixation as con- 

 trasted with the more artificial or man-controlled origin and fixation of 

 the cocoon characters, and that the evidence suggests the mutational 

 origin of the stable larval differences as contrasted with the origin of 

 the cocoon characters through the selection of fluctuating variations. 



However, this significance may not come to my readers with any 

 of the force with which it comes to me. If not I still wish to direct 

 their attention to the definite character, at least, of the differences in 

 consistency and regularity of the inheritance behavior of the two sets 

 of characteristics, and the inevitable conclusion that the heredity of 

 the silkworm is not to be expressed by any single fascinating sweeping 

 generalization as to its regularity. The longer the series of check lots, 

 the greater the opportunity the silkworm is given to reveal inconsis- 

 tencies in its heredity (that is, inconsistencies from our favorite point 



