460 WESLEY R. COE, 



plasm (shall we call it the secoodary ceotrosphere?) surrounding each 

 centrosome. They ramify in the reticulum of the centrosphere (Fig, 38) 

 much as the aster-fibres do in the cytoplasmic reticulum. This agrees 

 almost exactly with Geiffin's observations in Thalassema. Meanwhile 

 the growth of the centrospheres themselves has continued until they 

 have become nearly equal in size to the diameter of the spindle. In 

 this respect, and in their conspicuous vesicular structure they closely 

 resemble the centrospheres in a similar stage of the Echinoderm-egg. 

 The asters surrounding the centrospheres likewise continue to increase 

 in size until the egg begins to show indications of the cleavage 

 furrow. 



This seems to me to be a point worthy of special consideration. 

 We have here a case in which we find a pair of centrosomes with 

 delicate, radiating fibres within the centrosphere of another aster, the 

 rays of which continue to increase in length. This is not an individual 

 exception; all the eggs in the same stage show a similar structure. 

 If we are to assume that the aster-fibres are formed and maintained 

 under the influence of the centrosome, it is difficult to explain the 

 fact that the asters of a cell continue to grow after their centrosomes 

 have not only divided, but are engaged in forming secondary asters 

 in preparation for the next succeeding cell-division. 



In the early telophase the primary asters reach their maximum 

 development, and their fibres extend in all directions nearly to the 

 periphery of the cell. The enormous centrospheres gradually lose 

 their distinct outer boundaries and become much less sharply marked 

 off from the surrounding cytoplasm (Fig. 39). The aster-fibres are 

 very coarse, and are much branched peripherally, but become much 

 more delicate in the region of the centrosphere. Their inner ends 

 sometimes fade out directly into the reticulum of the centrosphere, 

 and this is further evidence that this body is partially formed from 

 the substance of the aster-fibres. At a slightly later stage, the fibres 

 are seen to be broken up into rows of granules at their extremities, 

 showing that the period of the degeneration of the asters has begun. 

 At the same time the egg becomes very much elongated, and a slight 

 constriction , marking the cleavage furrow , makes its appearance 

 (Fig. 39). 



The pair of "secondary" asters continues to increase in size within 

 each of the "primary" centrospheres until their rays reach out into 

 the surrounding cytoplasm. That the initial rays of the secondary 

 asters are built up out of the substance of the primary centrospheres 



