Artificial Parthenogenesis in Thalassema Mellita 14I 



generally been regarded as furnishing strong evidence of the per- 

 sistence of the cleavage centrosomes and their direct continuity 

 with the sperm center. The doubt expressed above has led me to 

 examine with great care the entire period in the normally fertilized 

 egg from the first appearance of the sperm aster to the establish- 

 ment of the cleavage amphiaster, and the results which I have ob- 

 tained from these observations are not in accord with Griffin's 

 description. He was confident that he had traced the sperm cen- 

 trosome continuously into the cleavage centers, and stated his 

 conclusion as follows: "In Thalassema, 'the pause' is of short dura- 

 tion, and while the asters are a trifle less distinct, they nevertheless 

 show clearly throughout, and the persistence of their focal cen- 

 trosome is easily demonstrated. *** In most instances the presence 

 of the centrosomes can be made out with comparatively little diffi- 

 culty. With the commencing fusion of the nuclei, the centrosomes 

 take up a polar position, and immediately become the centers of 

 renewed activity, for many additional rays commence to start up 

 about them. From the above it is quite evident that the cen- 

 trosomes persist entire throughout the whole critical stage where, in 

 so many forms, they have been lost sight of ('99j P- 59^)' 



The material upon which I have made my observations was 

 preserved at intervals of one minute throughout the entire period 

 in question, and the sections made from it are as nearly perfect 

 as sections can be. Contrary to Griffin's observations, I have 

 found a stage, just before the fusion of the pronuclei, when the 

 rays of the asters become exceedingly faint, if they do not disappear 

 entirely, and the most careful search fails to reveal the presence of 

 centrosomes. A little later, upon the reappearance of the rays, 

 the centrosomes of the cleavage amphiaster can be demonstrated, 

 lam convinced, therefore, that a critical stage exists in Thalas- 

 sema, as in many other forms, and at this time the continuity of 

 the sperm centrosomes cannot be followed. Kostanecki ('06), 

 in a very recent paper, has undertaken an elaborate attempt to 

 prove the universality of the origin of the cleavage centrosomes 

 (centrioles) from the centriole of the spermatozoon, and has con- 

 vinced himself "das im befruchteten Ei samtlicher Metazoen die 

 Centriolen der ersten Furschungsspindel die direkten Abkomm- 



