KARVOKINETIC FIGURES OF CENTKIFUGED EGGS. 1 03 



plane. The outer pole of the spindle is practically in contact 

 with the surface of the egg, which is slightly depressed at the 

 pole. The centrosome of the outer pole is smaller than that of 

 the inner pole. The astr?l rays cross very extensively opposite 

 the equatorial plane ; indeed, rays from the outer pole may extend 

 inward beyond the level of the inner pole, and rays of the latter 

 may extend nearly to the surface of the egg. In the spindle 

 itself, there is the usual distinction between mantle fibers attach- 

 ing the chromosomes to the two poles and central spindle fibers 

 running from pole to pole. The interfibrillar spaces are perfectly 

 clear. The only asymmetrical feature of the spindle is the some- 

 what smaller size of the outer pole and the difference in arrange- 

 ment of the rays at the two poles, owing to the proximity of the 

 outer pole to the surface of the egg. 



All eggs show great uniformity, but there may be slight differ- 

 ences between eggs of the same lot in the following respects : 

 (i) In some the outer pole is not actually attached to the sur- 

 face so as to produce a depression, but may be removed from the 

 surface by a distance of about twice the diameter of the outer 

 centrosome. There is thus a variation in the firmness of fixation 

 of the spindle at the animal pole. (2) There is some variation 

 in the intensity, that is, in the length and strength of the astral 

 rays, which appear less well developed in some cases than in 

 others. In all cases, they cross to a considerable extent in the 

 equatorial plane. 



The evidence that is to be presented is furnished by the results 

 of centrifuging the eggs at varying speeds and for various times. 

 To form a proper conception of what happens it is absolutely 

 essential to understand the effects of centrifugal force on the pro- 

 toplasm. In a previous paper I presented an analysis of this 

 subject and showed that the fundamental structure of the egg as 

 represented by the conformation of the ground substance is not 

 essentially modified by the centrifugal force ; it is at most some- 

 what distorted. On the other hand, the granules suspended in 

 the ground substance move through the latter in a central or 

 distal direction, depending on their relative specific gravities, and 

 arrange themselves in three strata : the stratum nearest the axis 

 of the centrifuge is of course of least specific gravity ; it consti- 



