Cuap. I. THE PURKINJEAN VESICLE. 475 
and on this score need not make any further remarks; but we can very properly 
instance some particulars in regard to the effect of heat and acids. <A full-grown 
ovarian ege, being thoroughly boiled to the centre by immersion in hot water 
for the space of three minutes, was opened, and portions of its contents from 
different depths put in the field of the microscope, when it instantly became evi- 
dent, that, throughout the whole yolk, every cluster of crystalloid entoblasts had 
fused its individual components, each one to its neighbor, so that, in connection 
with the greater transparency that had followed this reaction, it was almost impos- 
sible to distinguish any thing but a faintly polygonal light yellow mass. Acetic 
acid at first swells the ectoblast till it bursts, then produces an effect similar 
to that of water upon the mesoblast, and finally destroys the same with the 
entoblasts, after having rendered the whole very transparent. Caustic potash swells 
the ectoblast enormously, and then dissolves its contents very rapidly. Pressure 
produces a curious appearance, which has been mistaken by some for a normal 
feature of the entoblasts, namely, parallel fissures imtersected here and there by 
others obliquely transverse to them.’ 
SE CL LOUN: TeV. 
THE PURKINJEAN VESICLE. 
When treating of the egg as a whole, in its earlier stages, the primary phases 
of the Purkinjean vesicle were included, as necessary to the understanding of 
the character of the egg, when viewed in the light of a cell; and now that we 
wish to make a separate, special study of the Purkinjean vesicle, besides refer- 
ring to former pages,> a rapid recapitulation is by no means superfluous, m order 
that there may be continuity in the illustration of the subject. We have already | 
spoken of the Purkinjean vesicle as being originally a minute concretion of solid 
matter against the wall of the primary egg cell, which has no definite size at 
the time; also of its having no part in originating the egg cell; of its great} 
transparency; of the subsequent existence of a distinct wall around it, under a 
form sufficient to restrain its fluid contents from intermingling with the yolk; and 
1 See J. Miiller, Ueber d. glatten Hai, q. a., p. 38, kinjean vesicle, rather than apply to it the more 
and Rathke Entw. d. Schildkroten, p. 5. usual name of germinal or germinative vesicle. See 
2 It has already been stated above why we prefer Sect. 3, p. 463, note 1. 
to designate this part of the egg by the name of Pur- ® Comp. Sect. 1, 456. 
