496 THOMAS H. BRYCE. 



position it assumes in the egg-, relative to the cleavage 

 plane. If it lies outside the equatorial plate of the spindle 

 it passes unchanged into one of the blastomeres ; if it 

 lies within the field of the first spindle, it does not 

 actually unite with the chromatin of the female nucleus, but 

 its chromatin undergoes a marked relaxation. Tliough it 

 shows a marked resistance to the tractive forces, it is drawn 

 out and torn into several shreds. It thus passes undivided 

 into one of the blastomeres, and no chromatin elements 

 derived from it are found at the poles of the spindle. In 

 several cases where the nucleus lay exactly at the equator, 

 and the traction of the 2:)oles was nearly equal, it was 

 observed that the chromatin mass was much broken up, and 

 was torn into two parts. The cleavage of the cell body may 

 have helped to complete the division. The loosening of the 

 sperm chromatin mass in the first spindle seems to have 

 broken its power of resistance, for when the next division is 

 initiated, the two nuclei lying side by side in one of the 

 blastomeres unite in the equatorial plate stage, and the 

 chromatin of both is equally distributed in the next division. 

 The number of chromosomes is now different in the blasto- 

 meres, sometimes double, perhaps quadruple in some cases 

 (though an accurate count was not possible), as if the chromo- 

 somes of the sperm nucleus emerged in double number, 

 though the first division was suppressed. 



The sperm nucleus in the case where it has not lain within 

 the power of the spindle in the first division, may now, in 

 analogous fashion, be caught in the second division, to unite 

 later with the chromatin of one of the blastomeres of the 

 four-cell stage, or it may even pass over into the eight-cell 

 stage, as seen in living eggs by Boveri. 



Teichmann concludes that the radiations are derived from 

 the sperm ccntrosome as their starting point, and on the 

 supposition that the centrosome is introduced by the sperma- 

 tozoon into the Qgg, that it has suffered less from the chemi- 

 cal reagent than the nucleus. The centrosome behaves as 

 in ordinary fertilisation, the sperm nucleus is passive, and 



