DIFFERENT KINDS OF INHERITANCE 



BEHAVIOR. 



The silkworm is a very convenient animal with which to experi- 

 ment in matters of inheritance. The matings can be made with ease 

 and certainty. Many of the races have been bred pure for hundreds of 

 generations and are very stable and reliable. The characters available 

 for observation are well-marked and easy to describe and illustrate, and 

 represent inheritance in different well-marked life-periods of the animal 

 so that the inheritance of characters peculiar to one life-period can be 

 compared with that of characters of another life-stage. Finally the 

 animals can be reared in large numbers in comparatively limited space, 

 and thus extensive series and many repetition lots be obtained for a 

 basis for generalizations. 



This last point is one on which I wish to lay stress. My conclu- 

 sions as to the behavior in inheritance, especially as regards its uni- 

 formity or non-uniformity, of various silkvoorm characteristics would 

 have been quite different from ivhat they are at present if I had not 

 made use of numerous repetition lots. It is on the basis of these 

 repetition lots that my conclusions as to strain and individual 

 idiosyncrasies in silkzvorm heredity are based. 



It is perfectly plain from the results of my experiments (as well 

 as from those of Coutagne and Toyama, to be referred to in a moment) 

 that different silkworm characters behave differently in inheritance. 

 (At least this is perfectly plain unless some ingenious analyst like 

 Bateson by a combination of real analysis with added hypotheses of 

 "determiners," or what not, undertakes to make it not perfectly plain.) 



These different characters are those of various life-stages, as 

 larval, pupal, or adult, but they are not necessarily like or unlike each 

 other in their inheritance behavior on the basis of any distinction of 

 life-stage. They differ in inheritance behavior simply on the basis of 

 difference in characteristic. These inheritance behavior differences 

 consist in some characteristics being alternative (and usually essentially 

 Mendelian) in inheritance, as larval pattern (white, patterned, tiger- 

 striped and moricaud), cocoon color, etc., while others are particulate 

 or blend in inheritance. The former are discontinuous or non-inter- 

 grading variations or differences, the latter are fluctuating or con- 

 tinuous, as wing pattern of adults, richness of silk in cocoon, adhesive- 

 ness of egg, etc. 



