600 



SCIENCE. 



[N. S. Vol. I. No. 22. 



ant systems with tlieir surroundings. 

 This, however, Weismann and his followers 

 deny, though no proof whatever has been 

 offered that such is not the fact. Indeed, 

 it is probable that, so long as the ultimate 

 machinery of metabolism is beyond the reach 

 of ocular demonstration, there can be no 

 proof or disproof of the position assumed by 

 the performationists or Neo-Darwinists. 

 Such proof or disproof is, however, non- 

 essential, since we are forbidden by the first 

 principles of djTiamics to assume that trans- 

 formation of any living phj^sical sj'stem 

 whatever can occur without iuvolving some 

 forces or influences that emanate from the 

 external world.* The separation and eval- 

 uation of the internal and external forces 

 incident to the manifestation of life, in the 

 present state of our knowledge, and from 

 the very nature of the case, plainly tran- 

 scends the capacity of present available ex- 

 perimental methods in biology. The dis- 

 cussion as to whether ' acquired characters ' 

 are inherited can, therefore, have but one 

 outcome, since external forces can never be 

 excluded in considering the life-history of 

 any organism. 



Nageli, in seeking to account for the phe- 

 nomena of growth, gave us a most ingenious 

 jihysical hypothesis of the constitution of 

 living matter. This, later on, he modified 

 so as to develop an hypothesis of hereditarj' 

 transmission. But the micellse that were 

 representative of the germinal matter of a 



*" Some of tlie exponents of this [ijreformatiou] 

 theory of heredity have attempted to elude the dif- 

 ficulty of placing a whole world of wonders •n-ithiu a 

 body so small and so devoid of structure as a germ, 

 hy using the phrase structureless germs (F. Galton, 

 Blood-relationship, Proc. Roy. Soc, 1872). Now one 

 material system can differ from another only in the 

 configuration and motion which it has at a given in- 

 stant. To explain differences of function and develop- 

 ment of a germ without assuming differences of struc- 

 ture is, therefore, to admit that the properties of a 

 germ are not those of a purely material system." — 

 James Cleek-Maxwell, article Atom, Encijd. 

 Britan., 9th ed.. Vol. III., p. 42, 1878. 



species he isolated in the form of rows or 

 chains of micellse traversing the rest of the 

 . living substance of the organism, and called 

 it idioplasm. Here again the germinal mat- 

 ter was conceived as separate from that 

 forming the rest of the body. Mr. Spencer 

 supposed " that sperm-cells and germ-cells 

 are essentially nothing more than vehicles 

 in which are contained small groups of the 

 phj'siological units in a fit state for obeying 

 their proclivitj' towards the structural ar- 

 rangement of the species they belong to." 

 These ' physiological units' are neither 

 chemical nor morphological in character, 

 according to Mr. Spencer's system, but it is 

 admitted that their properties and powers 

 must be determined in some way by their 

 own constitution, conditions of aggregation, 

 and relation to the outer world. The views 

 of Nageli and Spencer are akin in certain re- 

 spects, but they still retain a certain amount 

 of resemblance to the older ones, namely, 

 those hypotheses which assume that the 

 forces of inheritance are lodged in certain 

 very small corpuscles formiug part only of 

 the germ or organism. These hypotheses 

 are also dj'namical in nature, and have been 

 worked out with the consciousness, in both 

 cases, that the mechanism of inheritance 

 must also be the one through which metab- 

 olism operates. Indeed, these two authoi-s 

 seem to be the first to have distinct! j' recog- 

 nized the necessity for such a supposition. 

 Later still, with the advent of the discov- 

 ery that the male nucleus was fused with 

 the female nucleus during sexual reproduc- 

 tion, it was assumed that the nuclear con- 

 tents were the only essential material bear- 

 ers of those hereditarj^ forces that shape 

 the growing germ into the likeness of the 

 parentage. With the development of this 

 idea the name of Weismann is perhaps most 

 closely associated. He has utilized the 

 facts of development, nuclear cleavage, ex- 

 pulsion of polar bodies, halving and subdi- 

 vision of chromosomes, etc., as the founda- 



