116 DR. E, feLEIN. 



but rarely, I have seen one or the other oil drop included also 

 in the deepest part of the blastoderm — solid granules of a yel- 

 lowish colour and of very various sizes (see fig. 1) . Some of 

 the last-mentioned elements appear in the specimens under 

 consideration, as if they contained perfectly black specks 

 (fig. 1), the number of which varies according to the size of 

 the yolk-granules they are contained in ; in the large yolk- 

 granules the black specks are grouped together in the centre. 

 In the blastoderm itself are found numerous yolk-granules 

 containing these black specks ; in fact, we are able to detect, 

 with great ease, in the blastoderm the former by the presence 

 of the latter, and in the same way we are able to state that 

 towards the surface of the blastoderm the yolk- granules and 

 their black specks decrease in size. Similar yolk-granules, 

 containing these black specks, may be detected in the 

 blastoderm also in later stages (see figs. 2, S, 4, 5). Already 

 Rieneck (1. c, p. 360) mentions the presence of yellowish 

 yolk-granules in the cells of the blastoderm of the more 

 superficial layers, and Oellacher^^ (1. c, p. 26) speaks of the 

 elements of the blastoderm as if feeding (on the yolk- 

 granules) "from mouth to mouth." 



I have mentioned above that the extreme marginal portion 

 of the germ does not rest on the surface of the yolk-sphere. 

 By this I mean that portion only which is, so to speak, over- 

 hanging the paragerminal groove, for I have to add now that 

 the substance of the germ extends below that groove out- 

 wards on the surface of the yolk. This extension of the 

 germ is, from the circumstance above mentioned, only a con- 

 tinuation of the deeper part of the germ. It consists of 

 the same granular mass, and includes also smaller or larger 

 yolk-granules ; it is thickest where it is attached to the germ, 

 and becomes thinner in proportion as it becomes more distant 

 from it (see fig. 1). This quasi-extraneous portion of the germ 

 I will call parablast, in contradistinction to the segmented 

 part or blastoderm of the authors, which I Avill term archi- 

 blast. These terms I do not use, however, in the sense in 

 which they are applied by His {' Entwicklungs geschichte 

 der Wirbelthiere : Entwicklung der Hiihnchens,' Leipzig, 

 1868) to the ovum of hen, for, according to His, parablast is 

 not a portion of the same substance of which the blastoderm 

 consists, but is a part of the white yolk. Parablast and archi- 

 blast in the trout's ovum, however, is one continuous mass, 

 i. e. one and the same substance, of Avhich only one portion 

 — blastoderm (Auct.) or archiblast, i.e. that lying in the 

 saucer-like depression of the yolk — undergoes segmentation, 

 whereas the second portion, parablast, not participating in 



