380 Erste Sektion: Cytologie und Protozoenkunde. Erste Sitzung. 



cially when the astral rays are in a state of contraction that several 

 fibres are apt to unite. Consequently the aster becomes more 

 conspicuous during caryokinesis than during the resting period, 

 when the component fibrils again separate. 



The presence of amorphous granules in the cytoplasm cannot 

 of course be denied; but they are metabolic products which appear 

 and disappear according to the physiological condition of the 

 cell; and, in my opinion, cannot be identified as formed living 

 substance. When those amorphous granules are abundant, they 

 obscure the reticular features of the cytoplasm, especially in 

 poorly prepared material, where even the fibrous network, itself, 

 may crumble into disconnected granules. 



The coalescence, as well as the Separation of the cytoplas- 

 mic fibrils, may be entire or partial, in which case vacuoles ap- 

 pear, which give the impression of an alveolar structure. That 

 many of the unformed metabolic substances within the cyto- 

 plasm may form emulsions, enclosing air bubbles, and other 

 gases, as well as fatty particles surrounded by albuminous mem- 

 branes like ä foam, may be readily admitted; especially as Ob- 

 servation confirms the statement. Very large bubbles of this 

 kind are seen in beautifully preserved ova of Clemmys, figs. 6 — 10, 

 12. But the presence of these bubbles, emulsified fats, yolk sub- 

 stance, or whatever eise it may be, does not necessarily make 

 the actual, living substance a mere emulsion, having an alveolar 

 structure. 



From the appearance of the astral rays, both in the dividing 

 cell and in the less typically arranged corresponding body, in 

 resting cells, known as the vitelline body, archoplasm and at- 

 traction sphere, as well as from the general appearance of well 

 preserved protoplasm, like that shown in fig. 33, d, pl. Ia, it is 

 difficult to adopt an} other view of protoplasm than that of the 

 reticular. It seems probable that the peculiar appearance of 

 archoplasm is due, at least in part, to the fact that, in sections, 

 we look at the cut ends of very fine fibers. 



Nature of Fibrils and Centrosome. Like the 

 fibrils, the centrosome appears to be capable of subdivision into 

 parts, and also of increasing in size by the agglomeration of gra- 

 nules. It can be resolved into a delicate network of interlacing 

 fibrils. When the fibrils contract, the minute granules coalesce 

 and form a larger, more conspicuous body. The occasional ab- 

 sence of a central granule, usually called the centrosome, is, there- 

 fore, not of much consequence, since it is the arrangement of the 

 fibrils, which is the visible expression of cytoplasmic structure. 

 Many recorded observations regarding the disappearance of the 

 centrosome, as for instance, in the fertilized egg of Ascaris, may 

 be due to this Separation of the component particles when the 

 fibrils are relaxed, as they are apt to be, after each mitosis. 



