Febkuaey 5, 1897.] 



SCIENCE. 



231 



these cytoplasmic elements arranged in defi- 

 nite ways, come into play, and in the power of 

 more or less rapid transition from one to the 

 other is to be found an explanation of the main 

 features of the phenomena, so far as the share 

 of the cytoplasm, as such, is directly concerned 

 in each process. 



The results of these examinations, together 

 with the author's unpublished work on Ascaris, 

 in which it was shown that the centrosome in 

 the Ascaris egg not only undergoes some peri- 

 odic changes in its bulk, but totally disappears 

 at a certain stage, were urged against the theory 

 that the centrosome is a permanent organ of 

 the cell. 



S. Watase. 



II. CENTROSOME AND AECHOPLASM. ^ 



A SUMMARY of the conclusions reached in 

 my work on the egg of the earthworm {Allolo- 

 bophora fcetida) follows : 



1. The attraction spheres, both male and fe- 

 male, are of cytoplasmic origin. 



2. The archoplasm is a specific substance, 

 and not a mere thickening of the cytoplasmic 

 network. 



3. The microsomes are morphological ele- 

 ments and not merely varicosities- of the cyto- 

 plasmic threads. They vary greatly in size, 

 and many of them are unmistakably independ- 

 ent of the cytoplasmic reticulum. 



4. Five observations were urged as evidence 

 that the archoplasm is a specific substance and 

 of a fluid nature. These observations were : 

 (1) the relatively rapid movement of the sub- 

 stance, (2) the changes in its distribution caused 

 by fixatives, (3) its transparent appearance in 

 the living egg, (4) the cytoplasmic reticulum is 

 not lessened by its aggregations, nor (5) dis- 

 turbed by its migration. 



Katharine Foot. 



III. centrosome and sphere in the ovarian 



STROMA OF MAMMALS. 



The cells of the ovarian stroma of some 

 mammals (dog, rabbit) appear to undergo a 

 peculiar change during pregnancy. The small, 

 indistinctly defined, elongated or polyhedral 

 cells are no longer seen, but their place is occu- 

 pied by polyhedral cells of many times their 



size. The nucleus of these cells is regular in 

 shape and contains numerous clumps of chro- 

 matin irregularly distributed. It does not 

 usually lie in the center of the cell, but is dis- 

 placed more or less toward one side. Around 

 the central region of the cell is observed a dis- 

 tinct condensation of the cytoplasm, which is 

 very conspicuous after double staining. It is 

 not sharply limited from the remainder of the 

 cytoplasm, but shades gradually into it. The 

 whole cytoplasmic network, especially around 

 the denser part of the condensation, shows a 

 more or less distinctly radiate structure, though 

 there are no distinct fibres. This structure 

 can often be traced almost to the periphery of 

 the cell. Within the condensed portion of the 

 cytoplasm, at or very near a point forming the 

 center of the radiate arrangement, lies a small, 

 deeply staining granule or, in some cases, two. 

 This granule is very clearly shown by the use 

 of Heidenhain's iron-haematoxylin, after which 

 it differs from all other extra-nuclear structures 

 in the cell in retaining the dark blue or black. 

 This body is undoubtedly a centrosome, and 

 the condensation of cytoplasm around it un- 

 doubtedly represents a 'sphere.' 



Now these cells are not preparing for mitosis, 

 and, as far as has been found, there is no evi- 

 dence of any future division. Whether the cells 

 are in process of degeneration and are replaced 

 by new cells after the period of gestation is 

 ended, it has been as yet impossible to ascertain, 

 but it is probable that they are not. Moreover, 

 the steps in the appearance of the centrosome 

 and sphere in these cells have not been observed, 

 so that it is not known just when or how they 

 first become visible. No trace of them has 

 been found, however, in the stroma of ovaries 

 from animals which are not pregnant or have 

 not recently borne young, nor has any evidence 

 of mitosis been seen in the stroma proper. 

 Mitotic figures are occasionally seen in the cells 

 of young corpora lutea. The functions of these 

 structures under these conditions is not clear. 

 The relation of the histological changes in the 

 ovarian stroma to pregnancy also needs further 

 study. 



The presence of the centrosome and sphere 

 in cells which are not undergoing mitosis pre- 

 sents a problem which is at present rather ob- 



