SC I EN C E.-SUPPLEMENT, 



FRIDAY, AUGUST 6, 1886. 



THE PHYSICAL BASIS OF HEREDITY. 



Professor Huxley, in his well-lmown essay, 

 has describpd protoplasm as the material sub- 

 stratum of all vital phenomena, and established 

 the term ' physical basis of life.' Recent investi- 

 gations lead to the hypothesis that there is a 

 special and visible substance, vphich is the ma- 

 terial substratum of hereditary transmission from 

 parent to offspring, and may be called, if we 

 choose to imitate Huxley, the physical basis of 

 heredity. The name of the substance is chroma- 

 tine, in reference to the special affinity for color- 

 ing-matters, vs'hich is the most striking character- 

 istic of the substance. 



Chromatine, also called nucleine by some 

 writers, is found in the nuclei of cells of all kinds. 

 It is only recently that it has been clearly recog- 

 nized, and a great deal of additional investigation 

 must be accomplished before we can hope to know 

 much about it. It was impossible to ascertain 

 much concerning it hitherto, because the methods 

 of preserving tissues for microscopical examina- 

 tion have become perfected only within the last 

 few years, so far that the minute details of cell 

 organization could be studied. Nor was it until 

 the recent introduction of oil immersion objec- 

 tives by Dr. Zeiss, that we had command of lenses 

 sufficiently perfect for the investigation of chro- 

 matine. For those who wish to inform them- 

 selves more fully concerning the occurrence and 

 peculiarities of chromatine, I refer to Carney's 

 'Biologic cellulaire,' which I venture to think the 

 best general work yet published on the structure 

 of cells. 



For our present discussion a very brief state- 

 ment will suffice. When cells, properly preserved, 

 are stained with almost any of the dyes common- 

 ly used by histologists for the coloration of cell 

 nuclei, the higher powers of the microscope reveal 

 the fact that the nucleus contains three visibly 

 different matters, — 1°, the network of slightly 

 colored threads ; 3°, some dots or threads very 

 deeply stained ; 3°, the hyaline, or granular sub- 

 stance, in which the other parts are embedded. 

 This basal substance, enchylema, is probably more 

 or less nearly fluid during life, and is equivalent 

 to the kernsaft of those German writers, who ap- 

 ply that term in its proper and restricted sense : 



unfortunately it is employed with a variety of 

 meanings. The network resembles the protoplasm 

 network of the body of the cells, and is probably 

 the intra-nuclear extension of the protoplasm. 

 The deeply dyed parts are the chromatine ; and 

 the presence thereof appears, so far as our present 

 knowledge goes, the essential and distinctive 

 characteristic of a nucleus. 



During the division of cells, in the great ma- 

 jority of cases, very remarkable changes occur in 

 the arrangement of the chromatine, leading to 

 the development of those striking appearances 

 known as karyokinetic figures, or, as Flemming 

 would like to have them called, mitoses. It is 

 difficult to refrain from styling the latter term 

 new-fangled ; for the systematic duplication of 

 terms with which Professor Flemming has unneces- 

 sarily burdened science of late can only be con- 

 demned. It is curious to encounter such pedantry 

 in so industrious and sensible a histologist, be- 

 cause to overvalue terminology is the mark of 

 mental poverty. As the figures in question are 

 described in the more recent text-books of anato- 

 my and histology very fully, we need allude only 

 to the conclusion that the nucleus appears to lead 

 the process of division, and the chromatine to lead 

 the division of the nucleus. Nussbaum (Arch. f. 

 mikros. anat., xxvi. 504) points out, however, that 

 in some cases the protoplasm apparently leads, 

 alterations in it preceding nuclear changes. He 

 refers especially to observations on Infusoria by 

 Everts (Zeitschr. wiss. zool., xxiii. 601) and Jickeli 

 {Zool. anz., 1884, p. 491). But to interpret such 

 observations, we must not forget that the nucleus 

 and protoplasm are interdependent, neither being 

 able to maintain its existence without the other, 

 at least in any instance where they are normally 

 united. The fact that the visible alteration of the 

 protoplasm in a certain rare case comes before 

 that of the nucleus shows that the protoplasm 

 probably has an active role in cell-division ; but 

 since even then its arrangement depends on the 

 position of the nucleus, the evidence of the 

 superiority of nuclear control is, I think, not 

 affected. 



On the other hand, there are many observations 

 which may be interpreted as proofs that the 

 nuclei have a regulating power over the cells, 

 especially as regards their division and organiza- 

 tion. A few of these may be instanced. 1°. After 

 a cell is formed, its nucleus enlarges first, and the 

 cell body follows it in growth. 3'^. KoUiker, in 



