Ookinesis in Ccrebratiilus Lacteus. 355 



constant size snspended in hyaloplasm.'' The former can readily 

 be seen in the living egg, while the latter can bo observed only in sec- 

 tions stained either with Delafield's hsematoxylin (which stains hyalo- 

 plasm only) or with iron-hsematoxylin, thoroughly extracted, and 

 erythrosin as a counter-stain. Very young eggs stain dark, since 

 they are made up almost entirely of hyaloplasm (cf. Wilson '99, p. 

 11). As I have not been able to make out any space between the 

 yolk drop and hyaloplasm, the yolk drop itself represents alveolar 

 substance, and is not contained in a distinct alveolar substance as 

 Coe maintains ('99, p. 434). The yolk drop of the nemertine egg 

 has, I think, a much greater power of withstanding the action of 

 acetic-sublimate than that of the echinoderm egg, in which, under the 

 same treatment, the alveolar substance is found completely dissolved. 

 It is extremely difficult to determine the relative viscosity of the yolk 

 drops and hyaloplasm. The latter, however, seems to me more fluid 

 than the former, for the reason that, when the egg is crushed, the 

 hyaloplasm flows out more readily than the yolk drops (Mrs. 

 Andrews, '97, p. 82; Wilson, '99, p. 7, and his PI. T, Fig. 7), and 

 the polocytes do not contain in our case any yolk drops at all. 



In the egg prior to the dissolution of the germinal vesicle one ob- 

 serves very readily, in sections as well as in the living state, that the 

 yolk drops are disposed radially (PL I, Fig. 1) (cf. Bambeke, '98, 

 Fig. 7, PI. 25, p. 537 ; Giardina, '02, pp. 564-565 ; Gerould, '06, p. 

 82). This arrangement may indicate some nuclear activity upon 

 the cytoplasm. After the germinal vesicle has faded this is dis- 

 turbed by the mixture of the nuclear fluids and cytoplasm; some of 

 the yolk drops pass into the nuclear area, while the nuclear fluid 

 flows out into the cytoplasm. Thus the cytoplasm becomes richer 

 in hyaloplasm even as far as the periphery, the yolk granules being 

 less crowded than they were before. The amount of hyaloplasm in 



^lu the living egg of ecliinodernis Mathews observed that the cytoplasm is 

 not alveolar but granular ('O(i). The term "alveole" has not been understood 

 as a "hole," as he defines it, (p. 143), and its contents, the alveolar substance, 

 differs markedly in the degree of viscosity ranging from thin watery drops 

 to highly viscous yolk granules, (cf. Mrs. Andrews, '97, p. 14). The term 

 alveolar may, therefore, be apijlied to the echinoderm egg without causing any 

 inconvenience. 



