22 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



tion division. Brauer therefore conteuds that a Weismannian reduction 

 is impossible in karyokiuetic division, and indeed never occurs. For 

 Brauer the reduction question has consequently found its final solution : 

 There is no reduction except merely one of mass. This would offer 

 a very simple answer to the problem. But Henking ('90, '91, '92), 

 Eiickert ('92, '93), Hacker ('91, '93), and vom Eath ('91% '92, '93) have 

 been able to see only one longitudinal splitting. I have seen no evidence 

 of any such splitting of the chromatic thread in Caloptenus. Since com- 

 ing to that conclusion, I have read in Bom's paper on the egg of Triton 

 ('94) that he finds a doubling in the number of the chromatic elements 

 during the germinative-vesicle condition, but this doubling does not 

 result from a longitudinal splitting. The chromatic thread divides 

 transversely into twice as many segments as there were chromosomes in 

 the Ureizelle. Born's statement that " eine Verdoppelung durch Quer- 

 theilung stattfindet " is in essential agreement with my results. 



A remark by Wagner ('92) — to the effect that twice as many 

 chromosomes arise during the resting stage immediately before the first 

 maturation division as were in the cells of the preceding generation, 

 but that this does not imply any such definite longitudinal splitting 

 as Brauer and other authors maintain — may also be interpreted as in 

 harmony with my conclusions. 



Since the chromatin in the resting stage is very finely divided, — at 

 least into finer particles than the " Chromatinkorner " to which Brauer 

 ascribes the dignity of individuality, — it seems to me just as arbitrary 

 to consider these homogeneous "Chromatinkorner" units, which by di- 

 vision must give rise to identical daughter grains, as to make the same 

 supposition with regard to the chromosomes. 



But further, even if we grant for a moment that the Vierergruppen 

 do arise by two longitudinal divisions of the chromatic granules, what 

 evidence have we that each Vierergruppe consists of four identical 

 elements 1 Brauer maintains that both these splittings take place very 

 early in the resting stage. The granules are extremely small. Each 

 chromatic quarter of the group increases considerably in size. This 

 growth takes place while they are separated (held together only by 

 linin threads). There is still the probability that chromatic substance 

 is formed in the nucleus during the process, and becomes associated 

 with the substance of the Vierergruppen. In order to insure the 

 identity of the elements of a A^ierergruppe, two longitudinal divisions 

 must take place after all growth of the chromatin has ceased, and we 

 must at the same time assume that the chromatic elements are homo- 



