562 BULLETIN OF THE 



" spot." The vitelline granules invade more or less this fluid substance, and 

 thus diminish the size of the clear space. " Presque aussitot se manifeste dans 

 cet espace un systeme radiaire, .... qui consiste en un corps fusiforme aux ex- 

 tremites duquel se voient deux soleils. Comment cette formation a-t-elle pris 

 naissance ? Pas plus que les auteurs qui m'ont precede, je n'ai vu naitre sous 

 mes yeux ce systeme de radiations." Notwithstanding a careful study of fresh 

 eggs in which the germinative spot was in a state of dissolution, no conclusion 

 was reached by Perez, except that this stage is of short duration. Acetic 

 acid, however, has sometimes shown in the germinative vesicle on the point 

 of dissolution a pale and ill-defined double sun in the midst of irregular frag- 

 ments coming from the spot (Fig. 8). " A slight pressure easily destroys this 

 system, which I have never seen displayed in eggs whose germinative spot, less 

 disintegrated, still allowed one to see its two nucleoli." 



It is clear from the foregoing that the supposed identity of the two 

 " nucleoles " with the corpuscles of the asters rests entirely on the negative 

 evidence that the " nucleoles " were not to be seen after the appearance of the 

 stars. It is not even shown that the corpuscles exist at the centres of the stars 

 in the early stage represented in his Fig. 8 ; and there is nothing in this figure, 

 unless it be the nearness of the two stars to each other, which is in the least 

 inconsistent with their having originated outside the nucleus (germinative vesi- 

 cle) ; for the outline of the latter is no longer visible, and the clear space 

 shown is not of necessity due exclusively to the substance of the vesicle. But 

 Perez says further, that as long as the " nucleoles " are distinguishable in the 

 spot, reagents only render them still more evident. When the spot becomes 

 confused, however, either the reagents do not cause any definite form to appear 

 (attributable to the fact that the objects are extremely fragile), or a double sun 

 is seen. Less satisfactory evidence of a direct continuity could hardly have 

 been presented. Confessedly there exists a stage in which, both before and 

 after treatment with reagents, no definite structure is discernible. How, then, 

 can it be possible for the " nucleoles " to persist as central corpuscles in the 

 stars ? 



Perez seems to have been equally unfortunate in tracing the further history 

 of these corpuscles. He has often observed in the unaltered egg, either at the 

 centre of one (Fig. 16) or of both suns, a very small nuclear body very slightly 

 refringent, and surrounded at a little distance by a vesicular wall, — a body 

 having, in a word, all the characters of a very young cellular element (p. 371), 

 and he subsequently (p. 372) says distinctly that it is possible to obtain all 

 the transitions from the condition presented in Fig. 16 (compare Fig. 48, a a', 

 of Limax) to the elements which are subsequently seen at the two extremities 

 of the spindle ; but unfortunately he has not figured such intermediate stages. 

 It is true that Fifjs. 15 and 18 are intended to show such intermediate condi- 

 tions, but these I believe to be figures of a much later stage than is supposed 

 by Perez. He says (p. 400) that Fig. 15 is from an egg which had not yet 

 produced the first polar globule. In that I think the author may be in error. 

 He has said at p. 363 : " On pent trouver dans le diverticule d'une Helice des 



