480 THE AMERICAN NATURALIST. ■ [Vol. XXXIX. 



chromosomes are assumed to split longitudinally into equivalent 

 halves, which are the facts in all vegetative or somatic mitoses 

 so far as is known, and the chromatin is distributed quantita- 

 tively. By the second method chromosomes were conceived to 

 split transversely so that one half is carried to each daughter 

 nucleus, and if the two ends of a chromosome differed in the 

 character of their fundamental elements (ids and determinants) 

 the chromatin would be distributed qualitatively. Weismann 

 prophesied in 1887 that this second type of nuclear division 

 (qualitative mitosis) would be found and ever since investigators 

 have steadily searched for a transverse division of the chromo- 

 somes. They have been reported in connection with the mitoses 

 of chromosome reduction both for animals and plants and the 

 history of these investigations forms an important part of the 

 subject of reduction phenomena. But the present interpretation 

 of these transverse divisions involves the consideration of factors 

 that were unknown to Weismann and are very different from the 

 significance assigned by him. The effect of Weismann's specu- 

 lations, as a stimulus to investigations in these lines can, how- 

 ever, hardly be overestimated. 



Botanical literature dealing with the two mitoses of sporogene- 

 sis presents a confusion of statements respecting the presence 

 or absence of a transverse division of the chromosomes. Stras- 

 burger has changed his opinion three times. In his early studies 

 Strasburger ('95) believed that the chromosomes divided longi- 

 tudinally in both mitoses of sporogenesis. Then, led by studies 

 of Mottier ('97) he concluded ('97b) that the fission of the chro- 

 mosomes in the second mitosis was transverse. Almost imme- 

 diately, however, Strasburger and Mottier reverted to the former 

 opinion that the chromosomes divided longitudinally, a view 

 which Strasburger maintained in his lengthy considerations of 

 reduction phenomena in 1900a. Finally in a recent paper 

 (: 04b) Strasburger gives a very different interpretation of the 

 events of the first mitosis (heterotypic), based on the study of 

 Galtonia, and in general agreement with the most recent conclu- 

 sions of Farmer and Moore (:03). Farmer ('95b), Farmer and 

 Moore ('95), Miss Sargant ('96, '97), Guignard ('99a), Gr^goire 

 ('99), Lloyd (: 02), and Mottier have also held that the divisions 



