STUDIES ON CHROMOSOMES 425 



viction of an exact order that underlies their superficial fluctua- 

 tions, and one of which the main outlines are steadily becoming 

 clearer. 



It appears to me that many of the recent cytological advances 

 support the view that the true key to this order was found by 

 Flemming when he chose the word 'mitosis' ('82), and by Roux 

 in his attempt to find the essential meaning of the mitotic process 

 ('83). This is well illustrated by the pre-synaptic phenomena 

 that have here been considered, and by the increasing body of 

 observations that emphasize the importance of the mitotic trans- 

 formation of the chromatin-substance. It is difficult to see what 

 meaning such processes can have if they do not involve a linear 

 alignment of different elements (substances) which are thus 

 brought into a particular disposition for ensuing processes of divi- 

 sion (Roux) or of paired association (Strasburger).^^ The practi- 

 cal utility of such a conception for the analysis of genetic prob- 

 lems has already become apparent. It is still only an hypothesis, 

 but one which we may hope sooner or later to see subjected to 

 definite experimental test. 



March 1. 1912. 



LITEEATURE CITED 



Agar, W. E. 1911 The spermatogenesis of Lepidosiren paradoxa. Quart. Journ. 

 Mic. Sci., n. s., no. 225, vol. 87, part I. 



Arnold, G. A. 1908 The nucleolus and microchromosomes in the spermatogene- 

 sis of Hydrophilus piceus. Arch. f. Zellforsch., Bd. 2, no. 1. 



Baltzer, F. 1909 Ueber die Entwicklung der Echinidenbastarde mit besonderer 

 Beriicksichtigung der Chromatinverhaltnisse. Zool. Anz., Bd. 5. 

 1910 Ueber die Beziehung zwischen dem Chromatin und der Entwick- 

 lung und Vererbungsrichtung bei Echinodermenbastarden. Arch, f . 

 Zellforsch., Bd. 5. 



Bateson and Punnett 1911 On the inter-relation of genetic factors. Proc. 

 Roy. Soc. Eng., B., vol. 84. 



Berghs, J. B. 1904 La formation des chromosomes h^terotypiques. II. 

 Depuis la sporogonie jusqu'au spireme definitif. La Cellule, tom. 21, 

 no. 2. 



1^ This point has been forcibly- urged by Strasburger (see '08, pp. 563-568; 

 '09, pp. 95-97). 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 13, NO. 3 



