564 Messrs. J. E. S. Moore and G. Arnold. Existence [Dec. 13, 



In later years several authors have drawn attention to the obvious 

 difference in size exhibited between one and another of the gemini on the 

 same spindle. And not infrequently one or more of the gemini, under the 

 title micro-chromosome or accessory chromosome, have been supposed to play 

 an individual and important part in matters connected with hereditary 

 transmission and the determination of sex.* 



Our attention has latterly been redirected to the exact nature of the first 

 maiotic (heterotype) division, owing to the fact that this form of mitosis has 

 been found to occur during the development of malignant growths in man.f 



In 1903, in conjunction with Professor Farmer, we were able, from an 

 extended series of observations, to elaborate a general scheme of the maiotic 

 process which appears to hold good throughout the higher animals and 

 plants.^ More recently we have dealt in detail over again and extended our 

 observations upon the maiotic process in mammals and amphibia ;§ this 

 revision having become apparently necessary, owing to the mutually 

 divergent accounts of the maiotic process recently published by Strasburger 

 and his pupils in relation to certain plants.|j 



A re-examination of mammals and amphibia has however confirmed 

 our original standpoint with respect to the maiotic process in these 

 vertebrates, and a similar confirmation has been given for plants in the case 

 of Dictyotacese by Lloyd-"VVilliams,H Gregory, and others. During the course 

 of these revisions we have been led once more to the questions associated 

 with the forms assumed by the gemini of the first maiotic division, and it 

 appears to us now that the existing conceptions regarding this matter have 

 become inadequate to meet the actual facts of the case. We do not at 

 present profess in any way to have reached a final standpoint in our concep- 

 tions of the nature of the different forms of gemini, but the phenomena that 

 have been brought to light are so remarkable in themselves, and from the 

 point of view of theoretical developments so peculiarly attractive, that we 



* For example, see Strasburger, " Typische und Allotypische Keruteilung.," ' Jalirb. f. 

 Wiss. Botanik,' vol. 42 ; O. Eosenberg, op. cit., and others. 



t Farmer, Moore, and Walker, " On the Eeseniblanees between the Cells of Malignant 

 Growths and those of Normal Beproductive Tissues,' 1 ' Boy. Soc. Proc.,' 1903. 



| Farmer and Moore, " New Eesearches concerning the Heterotype Divisions in Animals 

 and Plants," ' Eoy. Soc. Proc.,' 1903 ; Farmer and Moore, " On the Maiotic Phase (Seduc- 

 tion Divisions) in Animals and Plants," ' Quart. Journ. Micr. Sci.,' vol. 48. 



§ Moore and Embleton, " On the Synapsis in Amphibia " (loc. cit.) ; Moore and "Walker, 

 " On the Maiotic Phenomena in Mammalia," ' Thomson Yates Eeports,' University Press, 

 Liverpool, 1906. 



|| Strasburger (loc. cit.). See also Overton, Miyake, and Allen, 'Jakrb. f. Wiss. 

 Botanik/ vol. 42. 



H J. Lloyd- Williams, h Studies in the DictyotaceEe, I and II," 'Ann. Bot./ 1904. 



