58 KRISTINE BONNEVIE. 



Opposed to the apparently strong evidence in favor of a re- 

 duction division brought together in these papers, as well as 

 that from the valuable investigations of Schreiner (1906a) on 

 the maturation process in Tomopteris — my results on Entero- 

 xenos stood quite isolated. And the reasons which at an earlier 

 period had seemed strong enough to support my view, might 

 now seem inadequate. 1 Even before the appearance of my final 

 paper (1906) I therefore felt the necessity first of reinvestigat- 

 ing the maturation process in Enteroxenos and second, in case of 

 the confirmation of my earlier results of finding another object, 

 in which the behavior of the chromosomes might be more 

 easily followed than in this species. 



On reinvestigating my old isTz^TYur/zcs - -preparations as well 

 as new material of the same species, I found, that although it 

 might well be possible, even in this species, to select a series of 

 maturation stages showing the " Tomofiteris-type" (Schreiner, 

 1906a:), yet other structures are present in the chromosomes 

 which do not support the assumption of a reduction division. 



Besides the great similarity in the general appearance of the 

 two maturation divisions there is a longitudinal split in the 

 chromosomes at the end of this period — a structure which 

 suggests an interrogation as to the assumption of a reduction 

 division, until the existence of this mode of mitosis has been 

 proved for this very species. 



On the other hand, however, I willingly admit that Enteroxenos 

 is not a favorable object for a decision of these difficult questions 

 — the chromosomes being very much contracted during the 

 metaphase and so small, that the structures in question are often 

 beyond the limit of an objective demonstration. It therefore 

 seemed desirable to extend my investigations to other species 

 with more favorable chromosome relations. 



1 (Added on the proof-sheet, June, 1907. ) The truth of this sentence was clearly 

 proved through the appearance of the latest paper by A. and K. E. Schreiner ( 1907) 

 some weeks ago. Their results seem to prove that ' ' the new observations in my paper 

 were not good, while the good ones (if present) were not new." I hope however, 

 through this and my following publications to show that my main results on the 

 maturation divisions in Enteroxenos were correct, and that the doubt which they made 

 me feel with regard to the existence of a reduction division in this species was well 

 founded, even if future observations should show that my interpretation of the new 

 facts would have to be modified. 



