520 DEVELOPMENT OF THE SIMPLE TISSUES, BY S. STRICKER. 



mass, of which it cannot at present be stated whether it be- 

 longs to the germ or not. Oellacher has not been able to 

 recognize a germ- vesicle in sections made at this stage. 



The first groove in the germ was found in an egg that, ac- 

 cording to the laying-time of the hen, had remained for twelve 

 or fourteen hours in the oviduct. The body appearing to be 

 the germ was in the already described position, but was some- 

 what larger and thicker, a sinuous indication of fission of its 

 substance extended somewhat obliquely downwards from the 

 centre of its convex surface. 



The second groove was obtained from an ovum, the shell of 

 which already presented some traces of calcification. And 

 again, at the point at which the germ was to be sought, there 

 was a somewhat concavo-convex disk, which however appeared 

 to be thinner and larger than that of the earlier stage. Pro- 

 ceeding from the surface, five clefts penetrated into the interior, 

 splitting the disk into six areas on section. The two most 

 external areas were the longest, but the four middle ones did 

 not materially differ from each other. 



In this specimen it was impossible to state with certainty 

 whether there were other, though less defined, morphological 

 elements of the germ beneath the above areas. 



The next stage was taken from an eofff, the shell of which 



O OO 7 



was already consolidated, but was relatively \ery thin. The 

 germ was here sharply separated from the yolk, and there was a 

 distinctly perceptible cavity between the two. Sections through 

 the centre showed that the germ was composed of polygonal 

 areas, of which six could be counted between the surface and 

 the cavity. 



The whole germ, and this term could now be applied with 

 precision on account of the sharp definition of the mass below, 

 always presented an approximation to the form of a biconvex 

 lens, the upper surface of which was adherent to the vitelline 

 membrane, but the under surface of which was irregularly 

 bounded by the flat cavity existing between the germ and the 

 yolk. The marginal areas were the largest, and were filled 

 with larger granules than those more centrally situated. In a 

 few of the areas a nucleus was distinctly visible. 



At a subsequent stage, in an ovum also taken from the ovi- 



