Royal Microscopical Society. 195 



sizes. It is evident that these appearances are due to an amoeboid 

 movement of the blastoderm.* 



Soon after the blastoderm exhibits the appearances above men- 

 tioned, there is seen on its surface a median clear stripe, which by- 

 and-by becomes clearer ; this clear stripe represents the first furrow 

 of segmentation, by which the blastoderm becomes divided into two 

 halves. 



The blastoderm now seen from the surface appears as if notched 

 at two opposite points. 



Of the presence of the first furrow . we may convince ourselves 

 by looking upon the blastoderm in profile. If an egg on which the 

 first furrow has been made out in the surface view is looked at in 

 profile, which may be done successfully after some manipulation, 

 we may perceive that the blastoderm exhibits only in certain posi- 

 tions a notch, by means of which it appears to consist of two knobs 

 of equal size ; if we turn the egg round, we observe that the more 

 we approach an angle of 90^, as regards its previous position, the 

 more the notch displaces itself, so that the knobs become of unequal 

 size. If the angle of 90^ is complete, the surface of the blastoderm 

 appears quite smooth; that is, the blastoderm is now so situated 

 that the furrow lies horizontally. 



If we turn the egg again through an angle of 90^ the blastoderm 

 appears once more as if consisting of two knobs, that is, the blasto- 

 derm has such a position that the furrow stands vertically. 



A few hom's after the first furrow has appeared, there appears 

 a second furrow vertical to the former : the blastoderm seen from 

 the surface now exhibits a cross of clear lines, apparently such that 

 the two quadrants of the one half are smaller than the two qua- 

 drants of the other (see Fig. 3). The blastoderm seen in profile now 

 exhibits in aU positions a notch ; that is, it appears to consist of 

 two knobs. 



* Oellacher, in a recently-published paper about the germinal vesicle (Max 

 Schultze's ' Archiv,' 8 Bd. 1 Heft), says on p. 14, " That the germ (of trout) raises 

 itself from the yolk-groove shortly before the fecundation, contracts itself, and 

 spreads out again : that has Strieker described (' Wiener Sitzungsber. der K. 



Akademie,' Bd. 51) and has attributed it to active contraction I can only 



confirm these observations most decidedly." 



To the.se very decided assertions I have to add the following : — 



(1) Oellacher makes Strieker to say iiomething that Strieker never has said. 

 Strieker in the above-mentioned memoir concludes, from the peculiar appearances 

 wliicli chiomic acid preparations exhibit and which he (Strieker) mistook as 

 appearanct'S of segmentation, that the blastoderm possesses the power of active 

 movement, by means of which knobs grow up, which afterwards sep irate from the 

 main body. According to Strieker this proceeding forms a material part of the 

 segmentation. But that Strieker has said "that the blastoderm shortly befosie 

 THE FECUNDATION raiscs from the yolk-groove, &c., &c.," of that I cannot find 

 anything in the mentioned memoir. 



(2) I allow myself to doubt at once whether it is possible to observe contrac- 

 tions of the blastoderm on an unfertilized ovum of trout ; because, as I have 

 already stated, there is nothing io he seen of the blastoderm in the licinj condition 

 at this time, even not in the first hours after the fecundation. 



r 2 



