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8 Erste Sektion: Cytologie und Protozöenkunde. Erste Sitzung. 



trosome of the resting leucocyte, represented in fig. 17, and with 

 those of the dividing leucocyte represented in fig. 18? 



In fig. 24, a section of the egg of Limulus, a distinct astral 

 arrangement of the cytoreticulum is plainly visible. The absence of 

 distinct astral rays, as in fig. 25, pl. Ic may be due to the obscuring 

 effects of me meabolic products, which occur in all cells more or 

 less; and which is especially apt to be present in variable amounts 

 in egg cells, where stored food material is one of the chief causes 

 of the exceptional size of eggs, as compared with ordinary cells. 



The apparent disappearance of the aster in Ascaris after each 

 cleavage may be due to the obscuring effect of those amorphous 

 substances. As I have shown in plate Ic, the metaplasm moves 

 from place to place in obedience to the varying condition of ten- 

 sion or contraction of different cytoplasmic areas, possibly in the 

 same way as the granules in the cytoplasm of Amoeba move or 

 flow. Hence the aster may be entirely obscured or may stand 

 out very clearly, owing in part to the union of several fibrils, and 

 also in part to the radial arrangement of the amorphous sub- 

 stances. 



If other ovarian eggs be examined, we shall find correspon- 

 ding bodies in the cytoplasm with more'or less ease and certainty 

 according to our skill in preserving and preparing our material 

 for sectioning. The importance of such skill need not be empha- 

 sized; for clearly, these delicate structures require the most per- 

 fect fixation. 



In the resting cell, as the ovum in its long period of growth, 

 the astral rays separate apparently into ultimate fibrils that are 

 almost too delicate to be seen individually, with even the best 

 microscope. Even less perfect technique reveals this body in 

 the ovarian egg of the spider, fig. 26, pl. Ib ; of the frog, 

 fig. 27; in the fish, fig. 28; in crustacea, fig. 30; and in the 

 bird (dove) fig. 31. 



A body similar to these has been seen by, B a 1 b i a n i , 

 v. Wittich, Carus, Schütz, Julin, Mertens, 

 Henneguy, and by many other reliable observers. In many 

 cases, as in the crayfish, fig. 30, the body is usually found in a 

 notch of the nucleus where it is easily overlooked. 



I find a similar body in the cytoplasm of nerve cells of the 

 brain, fig. 21. It occupies a notch in the nucleus, and is apparently 

 the point of convergence of the many fibrils, permeating the cyto- 

 plasm of the multipolar nerve cell, and extending out into the 

 axons and dendrons of these cells. 



I have no more reason to suspect that these are temporary 

 arrangements of the fibrils, than that the fibrils of the cytoplasm 

 which extend into the neuraxon and spread out to form the den- 

 drons are so many temporary aggregations of amorphous granules. 



