PLATE 3 
EXPLANATION OF FIGURES 
The distribution of white and yellow yolk in the ova of vertebrata with special 
reference to zonal or lamellar formation. 
1 Egg of tortoise, Clemmys (from Munson, ’04), c.c. = cytocenter (centro- 
sphere); y.c. = inner cytocoel of Munson, and what I should call inner or first 
layer of white yolk; 7.y.l. = inner yolk layer of Munson, and inner or first yellow 
yolk layer I have called it: o.cy.c = outer cytocoel or second layer of white yolk; 
o. y. l. = outer yolk layer, or second layer of yellow yolk; s. c. 1. = subcuticular 
layer. 
2 Mature egg of Petromyzon (from Herfort, ’00). Very small granules in the 
external odplasm, gradually merging into the large granules and large vacuoles 
of internal odplasm. 
3 Nearly grown egg of Phascolarctus (marsupial) (from Caldwell, ’87). The 
darker crescentic body is coarsely granular yellow yolk; the clear area around the 
nucleus, which is also continued around the periphery of the entire egg is of finely 
granular white yolk. 
4 One end of large (3 em. long)egg of Bdellostoma (eyclostome) to show stratifi- 
cation of its yolk (from Dean, ’99). The fine curved lines represent points richest 
in minute yolk-spherules (white yolk). 
5 Mature egg of Ichthyophis glutinosa (amphibia) (from the Sarasins, ’87) 
6 X 9mm. with central ‘latebra’ of white yolk; this connects above with the germi- 
nal vesicle, forming a nucleus of Pander beneath the latter. 
6 Mature egg of Torpedo (from Riickert 99) in meridional section. The lens- 
like germ above. A central ‘latebra’ without stratification (Riickert says this is 
composed of dark, not light, substance). The dark layers are composed of loosely 
bound, but larger yolk platelets (white yolk?); the wider lighter strata of more 
closely packed but somewhat larger platelets (yellow yolk?). 
7 Hen’s egg photographed to show something of the concentric deposition of 
Sudan III. Dark lines = Sudan; these bright orange-red in original. The appear- 
ance here is very similar to the always less evident stratification of white and 
yellow yolk; the™narrow lines of Sudan in the photograph simulating the faint and 
narrow lines of the white yolk. 
8 Part of immature egg of Lacerta (from Sarasin, ’83) showing well-marked 
layers of white and yellow yolk (I infer that the dark lines represent white yolk); 
about one-fourth of egg is here shown. The germinal vesicle lies just outside the 
figure, above and to the right; all layers are seen to converge toward it, and to 
become gradually modified in its vicinity. 
490 
