LOSS OF EYE-PIGMENT 1N GAMMARUS. 303 
As the young in this figure (and in Fig. 2) were not all examined immediately 
on extrusion, the proportions given of normal-eyed to no-white-eyed cannot 
be regarded as exact. 
Fic. 2.— Mating of a normal Black carrying the factor jor Red with a Red No-white female 
~ (VIED) from a K Family brood not figured: with their F, and F, offspring 
(p. 326). 
Fig. 3.—Matings of Red and Black No-whites; Red male (RN) VII-E; with Red 
female (RN) VII.F; the same Red female with Black male (BN+R) VIIL.A- 
- of Fig. 1 (p. 328). VII-E. and VII.F. are from broods from K Family which 
are not figured. 
Fig. 4.—Mating of Red No-white with Albino No-white ; ¥, offspring all Red No-white ; 
F, offspring in the proportion of 3 Red No-white to 1 Albino No-white. The 
figure shows the first ten F,, broods from the inter-mating of the first F, brood. 
(See also p. 339.) 
Fie. 5.—Mating of Albino No-white or Colourless with Albino No-white ; offspring all 
Albino No-white. 
For details of this mating, see pp. 338 and 339. 
Plate VI. 
Albino carrying the factors for Black and Red crossed with Red No-white (see also Plate III, 
Fig. 6, p. 333); the Black offspring carry the factors for Red, Albino and No- 
white ; the Red offspring the factors for Albino and No-white. 
Fic. 1.—Mating of two of the Black offspring from the second brood of the above cross ; 
male a and female j (p. 333). 
Fic. 2.—Mating of two of the Red offspring from the second brood; male n and female x 
(p. 334). 
Fra. 3.—Mating of Black and Red offspring from the first brood of the above cross ; male 
a and female b (p. 335). 
Fie. 4.—WMating of a Red half No-white with Red No-white ; all the offspring normal 
Red-eyed (p. 340). 
The male is a red no-white descended from K Family. 
The female is an F, from the first mating of VI.A.1.h. (B+R-+A with R) 
(p. 293). Out of 25 young of the F, generation, two, a Red and a Black, were 
partly no-white when hatched. The Red one, figured here, had the Left eye 
no-white, the Right eye with the white reticulation present but thin ; this did 
not alter throughout its life. The Black one, when hatched, had the Left eye 
no-white, and only one streak of white in the Right eye. Two months later, it 
reached maturity, a female, and it was then found the Right eye had developed 
the perfect white reticulation all over, and the Left eye had also developed it 
over the upper half of its surface. 
Plate VII. 
All the figures from living specimens. 
Fie. 1.—Gammarus chevreuxt Sexton. Male. From a wild specimen. » 7. 
Fic. 2.—Normal Black Eye. B. x 58. ; 
Fic. 3.—Normal Red Eye. R. 58. 
Fria. 4.—Normal Albino Eye. A. from Female AB. (See p. 287.) 
Figured November 16th, 1915. x58. 
Fic. 5.—Red No-white. RN. 58. 
Fra. 6.—Colourless (Albino No-white. AN-+-R. See p. 339 for ancestry). 58. 
Fre. 7.—All-white perfect Eye. (See p. 287.) x58. 
NEW SERIES.—VOL, XI, NO, 3. DECEMBER, 1917. 2A 
