Ae: E. W. SEXTON AND M. B. WING. 
THE FIRST APPEARANCE OF THE RED EYES. 
Two pairs of Gammarus chevreuxi were taken in June, 1912, those re- 
ferred to in the previous paper as Pair I and Pair IJ. All four animals 
were black-eyed. 
All the broods from Pair IT were black-eyed. This stock (which is re- 
ferred to as the “‘ Pure Black ” stock) has been kept under observation 
from June, 1912, till now, December, 1915, fresh black-eyed material 
from the ditches being added from time to time. Not a single red- 
eyed animal has appeared in it. The strain was tested by mating also, 
to make absolutely certain of its purity before using it in the 
experiments. 
The first brood from Pair I were all black-eyed: 9 young ones coming 
to maturity, 3 males and 6 females. The first pair to mate (Pair A) 
were evidently the strongest, and had the largest broods, although owing 
to unfavourable conditions only a few in each brood survived. The first 
brood from this Pair A numbered 18 ; the young were counted on hatch- 
ing, but not examined for eye-colour ; of these 1 male and 6 females came 
to maturity, one of the females with red eyes. The second brood was 28 
in number, | male and 5 females surviving, and again one female had red 
eyes. For the third mating of the female A a different male was used 
(male 8), one which was freshly captured. The ensuing brood was ex- 
truded on October 26, 1912, 44 in number, and as these were being 
separated into finger-bowls for observation of moults 4 red-eyed ones 
were found. Male A was then put back with the female A, for the 
fourth mating; the brood numbered 39, 3 with red eyes. 
It will be seen that this female, mated with two different black-eyed 
males, produced some red-eyed young in each brood. No red eyes 
were observed in any of the other offsprmg of Pair I nor in their 
progeny. 
The four red-eyed young of the third brood died before reaching 
maturity, and the remainder of the brood were kept separate, each in a 
finger-bowl, until they were 66 days old. On December 31 they were put 
together in a bell-jar, and some mated at once. The first female to mate 
of this brood was separated from the others, and from her and her off- 
spring all the red-eyed stock has descended. 
By August 7, 1913, this female and its mate were dead, and only 20 
young were found in the jar, 16 black-eyed and 4 red-eyed. The four 
were removed, and the black-eyed left together for three months longer ; 
when again examined on November 5 the numbers were 65 black-eyed 
and 8 red, and with these work was commenced. 
