302 SOME PROBLEMS OF CELL-ORGAXIZATION- 



divide, in the reticulum of the spermatocyte-nucleus, they are very 

 numerous. His figures of the spireme-thread show at first nearly 

 forty granules in linear series (Fig. 120, />). Just before the breaking 

 of the thread into two the number is reduced to ten or twelve (Fig. 

 120, C). Just after the division to form the two tetrads the number 

 is four or five (Fig. 120, Z>), which finally fuse into a homogeneous 

 body.^ 



It is certain, therefore, that the number of chromomeres is not con- 

 stant in a given species, but it is a significant fact that in Ascaris the 

 final number, before fusion, appears to be nearly the same (four to 

 six) both in the oogenesis and the spermatogenesis. The facts re- 

 garding bivalent and plurivalent chromosomes (p. '^j) at once sug- 

 gest themselves, and one cannot avoid the thought that the smallest 

 chromatin-grains may successively group themselves in larger and 

 larsfer combinations of which the final term is the chromosome. 

 Whether these combinations are to be regarded as ** individuals " is a 

 question which can only lead to a barren play of words. The fact 

 that cannot be escaped is that the history of the chromatin-substance 

 reveals to us, not a homogeneous substance, but a definite morpho- 

 logical organization in which, as through an inverted telescope, we 

 behold a series of more and more elementary groups, the last visible 

 term of which is the smallest chromatin-granule, or nuclear microsome, 

 beyond which our present optical appliances do not allow us to see. 

 Are these the ultimate dividing units, as Brauer suggests (p. 113)? 

 Here again we may well recall Strasburger's warning, and hesitate to 

 identify the end of the series with the Hmits reached by our best 

 lenses. Somewhere, however, the series must end in final chromatic 

 units which cannot be further subdivided without the decomposition 

 of chromatin into simpler chemical substances ; and these units must 

 be capable of assimilation, growth, and division without loss of their 

 specific character. It is in these ultimate units that we must seek the 

 ** qualities," if they exist, postulated in Roux's hypothesis; but the 

 existence of such qualitative differences is a physiological assumption 

 that in no manner prejudices our conclusion regarding the ultimate 

 vioi'pJiological composition of the chromatin. 



D. Chromatin, Lixin, and Cytoplasm 



What, now, is the relation of the chromatin-grains to the linin-net- 

 work and the cytoplasm } Van Beneden long ago maintained ^ that 



1 Eisen ('99) finds that the chromosomes of the spermatogonia of Batrachoseps always 

 consist of six "chromomeres," each of which consists of three smaller granules or " chromi- 

 oles." The latter persist as the chromatin-granules of the resting nucleus; and it is through 

 their successive aggregation that the chromumeres and chromosomes are formed. 



2 '83, pp. 580, 583. 



