682 SCIENCE PROGRESS 



instead of splitting longitudinally, they divide transversely 

 across the middle. When the daughter cells are formed, it is 

 obvious that, as only half the number of chromosones appear 

 in this particular form of division, each daughter cell will contain 

 only half the number of chromosomes usually found in the cells 

 of the species of animal or plant from which it is derived ; 

 therefore the subsequent generations of cells, up to and including 

 the mature gametes or sexual elements, will also contain only a 

 half number of chromosomes. Thus when two gametes fuse in 

 the fertilisation of the ovum, the somatic number of chromo- 

 somes is restored and appears in the cells of the new individual 

 which is produced from it. 



It has already been pointed out that the only cells included 

 in the body of the multicellular organism which normally pass 

 out of somatic co-ordination as part of the physiological process 

 are the gametogenic cells — those of which the descendants are 

 destined to be separated from the body as gametes. In the 

 gametogenic cells which have passed through the meiotic phase 

 the number of chromosomes is reduced to half the usual (somatic) 

 number. Now the Meiotic Phase is noticeable also among the 

 cells of cancerous growths l and the observation of this pheno- 

 menon has a very direct bearing upon the view that the unique 

 characters of cancer are due to the fact that the cells have passed 

 out of somatic co-ordination. From the outset, the observations 

 recording the occurrence of the meiotic form of division among 

 cancer cells have been entirely misunderstood by many writers 

 and have consequently been subject to considerable misinter- 

 pretation. The characteristic feature of the meiotic phase is 

 the symmetrical reduction in the number of the chromosomes 

 to one-half of that found in the somatic cells. When this form 

 of division was first observed, before its real significance was 

 understood, the term "heterotype" was applied to it. Many 

 different kinds of abnormal conditions may influence the process 

 of division in ordinary somatic or body cells, causing them to 

 appear unlike those which take place usually. The chromo- 

 somes may be distributed asymmetrically among the daughter 

 cells, the consequence being that cells will produce with a 

 greater or less number than is normally observed. The chromo- 

 somes may also be crowded or clumped together in the form of 



1 Farmer, Moore and Walker, Proc. Roy. Soc. vol. lxxii. 1903 ; and B, vol. 

 lxxvii. 1906 ; Walker and Whittingham,/o«r«. Pathol, and Bact. vol. xvi. 191 1 



