SPECULATIONS UPON THE ORIGIN OF LIFE 641 



Every multicellular organism begins its existence as a single 

 cell, which in most cases is formed by the fusion of two cells, 

 one derived from each parent. This cell divides into two ; each 

 of these divides in turn and so on, until the whole body of the 

 organism is built up. Remembering what happens in cell 

 division, it is clear that every cell in the body, including those 

 that are to be cast off eventually to fuse with other cells and 

 form new individuals, must contain exact representatives of the 

 chromosomes contributed by the parents. This has led to the 

 very general assumption that the chromatin is the determinant 

 of the hereditary characters, the actual substance by which these 

 are conveyed. 1 The sexual act is held to consist essentially in 

 the union of chromatin from two distinct organisms. 2 



With these views I disagree most emphatically. To begin 

 with, it seems quite possible that the chromatin is merely a 

 secretion of the linin. It waxes and wanes at different times in 

 the same cell, particularly during certain periods preceding 

 division. If, however, it be true that chromatin is only a 

 secretion of the linin, the same claims would doubtless be made 

 for the latter substance. Unfortunately we know but com- 

 paratively little concerning it, beyond the fact that it forms an 

 envelope around the chromosomes, around the masses of chrom- 

 atin in the nucleus when in the vegetative state, a meshwork 

 between these masses ; also that it probably gives rise to the 

 nuclear membrane, in some cases at any rate. However, in 

 view of recent observations and experiments, neither linin nor 

 chromatin can be claimed as the sole or even chief means by 

 which hereditary characters are transmitted ; nor can the import- 

 ance of the fusion of two cells which constitutes sexual repro- 

 duction lie solely in union of the chromatin from two distinct 

 organisms. 



It has been shown that the chondriosomes divide individually 

 just as do the chromosomes. This has been traced from the 

 first segmentation of the ovum up to a late stage. They are 

 carried in the cytoplasm of the sperm and fuse with those in the 

 ovum, eventually forming the specialised cytoplasmic structures 



1 Strasburger, Hertwig, Kolliker, Weismann and others at different times have 

 advocated this view. See The Cell, Wilson, E. B., 1904; Heredity, Thomson, 

 J. A., 1908 ; Minchin, E. A , Science Progress, Oct. 1912. 



2 Weismann's theory of Amphimixis. Minchin, E. A., SCIENCE Progress, 

 Oct. 1912. 



