FLUCTUATING VARIATIONS AND THEIR INHERITANCE 4! 



tory an elaborate study of the inheritance behavior of this character 

 and will report on her work in another year. 



My own observations and experimental rearings on these various 

 fluctuating characteristics touch especially the following: degree of 

 adhesiveness of the eggs; subsidiary larval markings within the so- 

 called "white" and "patterned" types (which behave as a whole in 

 discontinuous and alternative fashion) ; wing pattern, and finally wing 

 venation. I shall discuss these characteristics briefly in the order in 

 which they have just been named. 



INHERITANCE OF EGG CHARACTER. 



The eggs of different silkworm races show differences apparently 

 constant in size, color and shape. But none of these differences has 

 seemed to me quite marked enough to be used in my studies ; at any 

 rate no attempt has so far been made to study the inheritance behavior 

 of any of these characters. 



But the character of adhesiveness (or lack of adhesiveness) is so 

 conspicuous and so readily and certainly determinable that it has been 

 made the subject of some experimental breeding. The one race in 

 my possession whose eggs are regularly (this regularity is not absolute) 

 non-adhesive is the Bagdad race, a strong white larva and white co- 

 coon race much used in the laboratory. Females of this race simply 

 drop the "non-sticky" eggs loosely in the mating boxes (small oblong 

 boxes made by folding and pinning square sheets of strong paper in 

 which the male and female to be mated are confined and in which the 

 female deposits her eggs). These loose eggs are like so many little 

 spherical seeds, yellowish at first but soon changing to lead-gray. The 

 eggs of all the other races I have are strongly stuck to the paper of the 

 boxes in a single layer with the eggs close together. Among the races 

 depositing adhesive eggs there is practically no female which fails to 

 fasten its eggs. Of course it would be quite possible for a female of 

 such a race to show the teratological condition of absence of cement 

 glands and such a one could of course not fasten her eggs. But in all 

 our rearings I do not recall a single case of the oviposition of loose 

 eggs by a female of an "adhesive egg" race. But the contrary is not 

 true. That is the females of the Bagdad race, the one non-adhesive 

 egg race that I have reared, show a certain degree of variation in 

 regard to this characteristic. This variation comprises the deposition 

 of eggs actually adhesive, that is fastened to the paper, but only 

 weakly so, that is, they may be displaced by gentle rubbing (it requires 



