462 WILSON. [Vol. XI. 



In the fully formed amphiaster the center of each aster is 

 occupied by a large, sharply defined, nearly spherical centro- 

 sphere, traversed by a rather open granular network. Its 

 substance is now left nearly unstained by hsematoxylin, but is 

 strongly colored by Congo red, so that, after double staining, 

 its contrast with the blue rays is very marked. During the 

 anaphase the centrosphere becomes still larger and finally 

 attains a truly enormous size, the maximum point being 



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s. 





n\^\ ^vu^\^"^^^ V ^x-ov^\ 







/ 



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# 



Fig. IX. — Cleavage in progress. Reconstruction of tiie daughter-nuclei. The chromosomal 

 vesicles have conjugated, leaving only two larger vesicles on one side and three on the other ; 

 these now lie in the shrunken remains of the centrosphere. Z. Group of granules (degenerated 

 spindle-fibres) forming a transitory " Zwischenkorper " or mid-body. \_cf. Phototype 10.] 



reached at the time the daughter-chromosomes attain the 

 limit of the spindle (Phototype 8). During the reconstruction 

 of the daughter-nuclei the centrosphere again undergoes a 

 remarkable metamorphosis. As the chromosomal vesicles are 

 formed the border of the centrosphere becomes somewhat 

 vague and its substance again assumes the blue-staining 

 capacity, so that the whole body is difficult to see (Phototype 

 9). As the chromosomal vesicles conjugate, the centrosphere 

 rapidly diminishes in size, its outlines become irregular, it 

 extends more or less completely around the chromatic vesicles, 



