368 Maternal Inheritance and Mendelism 



of them being uniform in their characteristics. When oviposited, they 

 were light greenish yellow and much lighter in colour than the ^i and 

 gradually assumed a brownish colour which finally turned a greenish 

 slate. Although they resemble the F^ eggs very much in colour, they 

 are darker and the colours are more decided than the latter, and have 

 no dirty or dull shade which is common in the eggs of Theophila. The 

 shell is of clear greenish yellow and deeper than that of the .^i or pure 

 wild forms. Therefore, we may easily distinguish F^ eggs from F^ eggs. 

 There are, however, certain variations of colour in the same batch or 

 between different batches, but no trace of the colour-characteristics 

 of the domesticated parents, and consequently we may say that the 

 colour-characteristic derived from the wild parent dominates over that 

 from the domesticated parent. 



In the spring of 1906, we reared worms derived from the F^ eggs. 

 Owing to the prevalence of grasserie and diarrhoea, all of them died 

 without attaining their mature stage. It will be noted here that, as far 

 as our experiments went, the hybrid form is much more easily injured 

 by those diseases than the pure domesticated form, especially in the 

 case where the male parents were of the wild form. It is, therefore, 

 very difficult to rear a good supply of the hybrid form for experiments. 

 We were therefore compelled to continue our experiments with back- 

 crossed form paired with domesticated one which is healthier than the 

 first cross. 



Back-crosses. 



In the summer of 1905, cross-bred moths from the ^i eggs were 

 mated with pure domesticated ones. Reciprocal matings gave, as in the 

 case of Fi, diametrically opposite results. Four Fi females mated with 

 pure domesticated males gave all greenish slate eggs whose colour 

 is quite the same as that of the F^ eggs before mentioned, while those 

 laid by 12 domesticated females (tetravoltine white) mated with the 

 cross-bred Fi males produced, without exception, eggs with character- 

 istics quite maternal. 



The worms derived from the former matings all died in consequence 

 of the two diseases above mentioned, while those from the latter, being 

 much more able to resist those diseases, gave some moths in the end of 

 the autumn of 1905, that is to say, the third brood of 1905. 36 batches 

 of eggs resulted from the inter se breeding, in which we found many 

 different coloured batches as is shewn below : 



