The Spermatogenesis in Pentatoma up to the Formation of the Spermatid. 49 



present up to the stage of metakinesis , since after or at that stage, 

 when the centrosomes separate, it may be clearly seen. The size of 

 the centrosomes is much greater than in the spermatogonic mitoses, 

 and my figures do not represent them too large. They are well- 

 marked, spherical bodies, apparently homogeneous, which stain deeply 

 with saffranine, but are scarcely at all differentiated by the use of 

 haematoxyline-eosin or the Ehrlich-Biondi stain. The various spindle 

 fibres pass with great clearness to their very surface, but there is no 

 specially differentiated portion of the spindle in their neighborhood 

 (no attraction sphere nor microcentrum). It is noteworthy that they 

 are larger in cells of the large than in those of the small generation, 

 since this would show that their volume would vary directly with the 

 amount of the cytoplasm. And since they do not appear to divide 

 simultaneously, they may be conceded a certain independence of action. 



Before the monaster stage is completed, a line joining the two 

 centrosomes of a pair may be at right angles to the axis of the 

 spindle, but more frequently either coincides with it or cuts it at an 

 acute angle; while in the completed monaster the axis of the one is 

 usually perpendicular to that of the other. From this it may be 

 concluded that the axis of division of each centrosome at first nearly 

 or quite coincides with the axis of the spindle and that it sub- 

 sequently turns so as to make an angle of 90 ° with the latter. 



When the centrosomes are at opposite poles of the spherical or 

 oval nucleus, a remarkable morphological peculiarity becomes apparent, 

 which to my knowledge has been remarked only by Henking (spermato- 

 cytes of Fyrrlwcoris). At that point where the centrosome lies the 

 nuclear membrane projects out to meet it in the form of a little cone 

 (Figs. 151—153, 156, 158, 159). This relation is apparent in all 

 cells of the large generation (Figs. 151 — 153), and in most of those 

 of the small. Each conical projection may or may not quite reach 

 to the centrosome ; the nuclear membrane on the surface of the pro- 

 jection has the same structure as at other points. Enclosed within 

 this projection lies a structure not noticed by Henking: this is a 

 mass of substance (w. Figs. 151, 152, 155, 158, 159), as seen on cells 

 fixed by Hermann's fluid, of nearly homogeneous appearance, without 

 a sharp outline, slightly refractive, and which does not become stained 

 by Hermann's method though shghtly browned by the action of osmic 

 acid. The volume of the substance varies, even the opposite masses 

 of substance of the same nucleus may vary in amount. Its shape 

 also is irregular it may be more or less conical or rounded, but more 



Zool. Jahrb. XH, Abth. f. Morph. a 



