R. C. PUNNETT 235 



can be arrived at, and the matter must remain open until more material 

 has accumulated. The data with regard to coupling and repulsion in 

 animals are still scanty and in most cases sex is one of the characters 

 concerned. Morgan's experiments with Drosophila (7) suggest coupling 

 of some kind between factors for eye colour and shape of wing, though 

 both of these factors may shew sex-limited inheritance in other families. 

 Hagedoorn (4) has described a case of what may be termed complete 

 repulsion between the factors for agouti and for colour in mice, but so 

 far as I am aware no other instance of repulsion or coupling between 

 characters independent of sex has yet been met with in the vertebrates. 



The chocolate series. 



Mention was made above (p. 233) of a chocolate buck which has 

 been used extensively for purposes of testing during the course of these 

 experiments. This animal was very kindly sent to me from Holland 

 by Dr Hagedoorn in the spring of 1910. It proved to be heterozygous 

 for Himalayan, a fact not without interest in view of Dr Hagedoorn'.s 

 statement that the chocolate colour was first met with in this variety 

 ((4), p. 107). My various experiments with this animal have amply 

 confirmed Hagedoorn's view of the recessive nature of chocolate as 

 opposed to black. In the course of the experiments I have made the 

 chocolate bearing the agouti factor, the so-called cinnamon (PI. XIII, 

 fig. 3) ; also the dilute chocolate which lacks E and corresponds to 

 the tortoise in the black series. This dilute chocolate, which, following 

 Hagedoorn, may be termed orange (PI. XIII, fig. 1), is of a clearer richer 

 colour than the ordinary yellow rabbit (PL XIII, fig. 2). The belly is 

 also orange, whereas in the dilute cinnamon it is white. Otherwise 

 these last two are not readily to be distinguished from one another. 



Corresponding to the agouti-black there is a form in the chocolate 

 series which may be called the deep cinnamon. This is a cinnamon 

 which is heterozygous for the factor D, and, as the illustration shews 

 (PI. XII, fig. 3), it is almost as deep in colour as the pure chocolate. 

 Analogy with the black series would lead us to expect the deep 

 cinnamons which are homozygous for D to be similar to chocolates 

 in appearance, but whether this is so or not I cannot say as I have not 

 yet been able to make the necessary experiments. 



There is one further point of interest in connection with the effects 

 produced by the factor D. A rabbit which is heterozygous for D and 

 is at the same time heterozygous for black (B) is an agouti-black, but 

 of a distinctly different type to one which is homozygous for B. The 



