40 



NATURE 



{Nov. 14, 1889 



capable, not only of compelling complex instinctive 

 actions occurring at one time of life, but of so successively 

 changing as to be able successively to make necessary 

 the successively occurring very different instinctive actions 

 of different periods of life, as e.g. in Sitaris. But this is by 

 no means all. The arrangement of the molecules must be 

 such as not only to effect all this, but also all the consti- 

 tutional pathological inherited modifications which are to 

 arise at different periods of life, and all the capabilities 

 of reaction upon stimuli of every cell, of every tissue, 

 and every predisposition an organism may possess — 

 "predisposition" and "capacity" being nothing more 

 than names for a certain collocation of particles so built 

 up as inevitably to fall down into other collocations — upon 

 shock and impact — the original collocation again being 

 such as to insure not only that the first ensuing collocation 

 from impact shall be of an appropriately definite kind, but 

 that its definiteness shall be such as to insure that all the 

 succeeding varied collocations from successive impacts 

 shall also be appropriately definite. I confess I do not 

 believe that such a collocation of particles is possible.^ 



This, however, is, after all, only a portion of the difficulty 

 from complication, necessarily involved in Prof. Weis- 

 mann's hypothesis of germ-plasm. For we have to consider 

 the modifying effect on the germ-plasm produced by its 

 effecting those developmental changes which it is its 

 own business to effect. After speaking of the great 

 complexity of the germ-plasm in higher animals, he goes 

 on (p. 191) to say: — "This complexity must gradually 

 diminish during ontogeny, as the structures still to be 

 formed from any cell, and therefore represented in 

 the molecular constitution of the nucleoplasm, become 

 less in numbers ; . . . the complexity of the molecular 

 structure decreases as the potentiality for further deve- 

 lopment also decreases, such potentiality being repre- 

 sented in the molecular structure of the nucleus." 



According to the hypothesis, the whole organism at 

 every stage of its existence is but a collocation of mole- 

 cules of different sizes most complexly arranged. Amongst 

 them, during development, are the portions of germ- 

 plasm, everywhere building up the increasingly complex 

 structures of the developing body, while they themselves 

 are simultaneously decreasing in complexity of compo- 

 sition. Now, it seems somewhat difficult to conceive of 

 such a mass, which may thus be said to both decrease 

 and increase simultaneously in complexity, both centri- 

 petally and centrifugally, and yet to preserve its com- 

 plexity both centrally and sporadically, as must be the 

 case in order to effect sexual reproduction and such repair 

 of tissues after injury, as the organism may be capable of 

 Prof Weismann continues : — " The development of the 

 nucleoplasm during ontogeny may be, to some extent, 

 compared to an army composed of corps which are made 

 up of divisions, and these of brigades, and so on. The 

 whole army may be taken to represent the nuceloplasm of 

 the germ-cell : the earliest cell-division (as into the first 

 cells of the ectoderm and endoderm) may be represented 

 by the separation of the two corps, similarly formed, but 

 with different duties : and the following cell-divisions by 

 the successive detachment of divisions, brigades, regi- 

 ments, battalions, companies, &c. ; and as the groups 

 become simpler so does their sphere of action become 

 limited. It must be admitted that this metaphor is im- 

 perfect in two respects : first, because the quantity of the 

 nucleoplasm is not diminished, but only its complexity ; 

 and, secondly, because the strength of an army chiefly 

 depends upon its numbers, not on the complexity of its 



' Prof. Weismann sees clearly enough the fatal complexity of the parallel 

 hypothesis of Nageli, who would explain all this by "conditions of tension 

 and movement." " How many different conditions of tension," our author 

 remarks (p. 182), " ought to be possessed by one and the same idioplasm, in 

 order to correspond to the thousand different structures and differentiations 

 of cells in one of the higher organisms? In fact, it would be hardly pos- 

 sible to form even an approximate conception of an explanation based upon 

 mere conditions of tension and movement." 



constitution." A better illustration of the Professor's con- 

 ception would seem to be that of an army very complexly 

 organized sending off successively regiments of different 

 kinds, but always retaining in the centre a few men of 

 all arms, and always being recruited by rustics (the food 

 of the germ-plasm), who become organized by the central 

 reserve of all arms retained for that purpose. 



But how, according to this or any other conceivable 

 illustration, are we to understand the germ-plasm becom- 

 ing simplified by forming tissues and organs, and then 

 regaining its complexity so as to be able to effect the 

 various reparative growths which constantly take place 

 after non-fatal injuries ? Or if we are to deem that the 

 germ-plasm only regains a portion of its complexity — one 

 portion in one place, another in another — how can we 

 conceive of the germ-plasm being so divided that each 

 part of the body has just that portion of germ-plasm 

 which is needed for its reproduction, in spite of that being 

 the very portion which we might expect to have been 

 exhausted, since it is it which has built up that part of 

 the body. 



Moreover, all these processes of succession, 'pro- 

 gression, simplification, and possible recomplication, of 

 the germ-plasm itself, must, according to the hypothesis, 

 have been laid down and necessitated in the first original 

 collocation of the molecules of the germ. This seems to 

 me to exceed the bounds of credibility.^ 



But if the hypothesis of germ-plasm be deemed one 

 involving too much complexity for belief— that is, if the 

 conditions supposed by it are deemed inadequate to explain 

 the results of sexual ontogeny — the hypothesis seems yet 

 more unsatisfactory with respect to processes of repara- 

 tive growth and reproduction by gemmation. This is a 

 subject the Professor has not yet expressly treated, and 

 therefore some suggestions with respect to its dif^culties 

 may be welcome to him, as showing what elucidations 

 some minds seem to require. He, however, tells us (pp. 

 197, 211, and 322) that such processes of growth are due 

 to the presence of germ-plasm, and of course not so to 

 hold would be to abandon his hypothesis. It is, however, 

 difficult to understand how we can thus account for the 

 reproduction of a human elbow with a joint structurally 

 and functionally much as the old one (see " On Truth," 

 pp. 170-17 1). Are we to understand that germ-plasm in 

 all its complexity was there ? If so, is it universally dif- 

 fused through the organism as well as present in the sexual 

 glands, and why does it not produce rather an embryo 

 than an elbow-joint ? linof, how comes it that the germ- 

 plasm present happened to have the complexity needed 

 to effect that which was, anatomically and physiologic- 

 ally, effected ? With respect to germination generally, the 

 Professor says (p. 322) :— " The germ-plasm which passes 

 on into a budding individual, consists, not only of the 

 unchanged idioplasm of the first ontogenetic stage (germ- 

 plasm), but of this substance altered so far as to corre- 

 spond with the altered structure of the individual which 

 arises from it, viz. the rootless shoot which springs from the 

 stem or branches. The alteration must be very shght, 

 and perhaps quite insignificant, for it is possible that the 

 difference between the secondary shoots and the primary 

 plant may chiefly depend upon the changed conditions of 

 development,^ which takes place beneath the earth in the 

 latter case and in the tissues of the plant in the former." 



' The term " Zielstrebig," as one used to denote a practically teleological 

 process which is not really teleological, is a remarkable example of the mode in 

 which we are led to regard the invention of a new name as an explanation. 



2 The remarkable readiness with which the fertile mind of Prof. Weismann 

 excogitates hypotheses on hypotheses to explain away difficuhies is rather 

 remarkably shown by the way in which he tries to obviate the objection to 

 his view as to parthenogenesis, which arises from the fact that in the bee the 

 same egg will develop into a drone or not. according as it has or ha3 not 

 been fertilized. This would seem to emphatically contradict his doctrine, that 

 the one cause of parthenogenesis is the greater amount of germ-plasm which 

 exists in parthenogenetic eggs than in ordinary ones. He meets this by sug- 

 gesting (p. 237) that if the spermatozoon reaches the egg it may, iinder the 

 stimulus of internal causes, grow to double its size, thus obtaining the 

 dimensions of the segmentation nucleus." What may not be thus explained? 



