May 31, 1895.] 



SCIENCE. 



SO* 



A DYXAJIICAL HYrOTHESIS OF IXHERI- 

 TAXCE.*i 



The doctrine of the preformation of an 

 organism in the germ is as inconsistent 

 ^vith the fact as with the reqnirements of 

 dynamical theory. The effects of the pre- 

 conceptions of preformationism have been 

 only too apparent in framing hj-potheses of 

 inheritance. The now dominant hypothe- 

 sis is simply an amplification, in the light 

 of numerous modern facts, of the preforma- 

 tionism of Democritus. He siipposed that 

 almost, infinitesimally small and very nu- 

 merous bodies were brought together in the 

 germ from all parts of the body of the par- 

 ent. These minute representative corpuscles 

 were supposed to have power to gi'ow, or 

 germinate, at the right time, and in the 

 right order, into the forms of the parts and 

 organs of the new being. In this way it 

 was supposed that the characteristics of the 

 parent were represented in a latent form in 

 the germ, which might grow as a whole, by 

 the simultaneous and successive develop- 

 ment of the germinal aggregate composed, 

 so to speak, of excessively minute buds, or 

 rudiments of the organs. In such w^ise also 

 did the successors of Democritus, namely, 

 Aristotle, Buflfon, and Erasmus Darwin, 

 suppose that the inheritance of parental 

 likeness by oftspring was to be explained. 

 The later and greater Darwin greatly am- 

 plified this hypothesis and proposed, pro- 

 visionally, to account for the phenomena of 

 inheritance by its help. Conceiving the 

 process somewhat as above supposed, he 

 consistently gave to his provisional hypoth- 



*From 'The Biological Lectures ' of the Marine 

 Biological Laliorator.v, Vol. III., 1S95. Printed from 

 the proofs by the courtesy of the editor, I'rofessor 

 Whitman. 



t It is interesting to note that the views developed 

 in this lectnre lead to conclusions in some respects 

 similar to those held by Professor Whitman in his 

 discourse entitled : ' 'Hie Insufficiency of the Cell- 

 Theory of Development,' publislied in the series of 

 lectures delivered in l^OS. 



esis the name oi pangeneiig, since the minute 

 latent buds of the germ were supposed to 

 come from, and thus represent potentially 

 everj"^ part of the bodies of the parents, and 

 possibly of still remoter ancest^J^ 



With the discovery of the presence of 

 germinal substance in multicellular organ- 

 isms, from the eml>rj-onic stages onwards, 

 by Owen, Galton, Jiiger, Nussbaum and 

 others, the theory of continuity of germinal 

 matter came into vogue. Upon this basis 

 Weismann distinguished two kinds of 

 plasma in multicellular beings, namely, the 

 germ-plasm and the body-plasm, and at 

 first assumed that because of this separation 

 the latter could not modify the former, 

 since the fate of the respective sorts of 

 plasma was predetermined by virtue of this 

 separation. The one kind was the mere 

 carrier of the other, and the germ-plasm 

 was immortal because it was produced in 

 each species from a store of it which always 

 existed, either in a latent or palpable form, 

 from the verj' beginning of development. 

 He seems, however, in recent j'cars, to have 

 admitted that this germ-plasm could be in- 

 directly modified in constitution through 

 the influence of the body-plasm that bore 

 and enclosed it. Beyond this point Weis- 

 mann again becomes a preformationist, as 

 truly as Democritus, in that he now con- 

 jectures that the supposed innumerable 

 latent buds of the germ, representative of 

 the organs of the future being, are minute 

 masses which he sees as objective realities 

 in the chromosomes of the nuclei of the sex- 

 cells. These chromosomes of the germ he 

 calls ' ids ' and ' idants,' according to their 

 condition of sub-division, and supposes them 

 to grow and become divided into ' deter- 

 minants ' and ' biophors' in the course of 

 embryonic development. To these he as- 

 cribes powers little short of miraculous, in 

 that he asserts that these infinitesimal 

 germinal particles grow and divide Just at 

 the right time and order, and control de- 



