XI.] PROBLEMS OF THE DAY. 85 



come converted into the somatoplasm (!) of the embryo, /or the 

 simple reason that it has ceased to be germ-plasm, and must there- 

 fore have lost the properties characteristic of that substance. 

 Neither can it be discharged by that portion of the germ-plasm 

 of the ovum which is aggregated in the germ-cells of the em- 

 bryo, for under these circumstances it is withdrawn from all 

 direct relation with the developing somatic cells. The question 

 remains without an answer '.' 



I believe, however, that the answer is to be found above. I 

 know nothing of the 'somatoplasm' of Professor Vines: my 

 germ-plasm, or idioplasm of the ist ontogenetic stage, is not 

 modified into the ' somatoplasm ' of Professor Vines, but into 

 idioplasm of the 2nd ontogenetic stage, and then into that of 

 the 3rd, 4th, 5th, and so on up to the looth and loooth stage ; 

 and each stage of idioplasm confers its own specific character 

 upon the cell in the nucleus of which it lies. 



Professor Vines also criticises my views as to the idioplastic 

 nature of the nuclear substance (the chromatin granules in the 

 nuclear loops, &c.). He maintains that it is as easy to speak of 

 the continuity of the cell-body as the continuity of the nuclear 

 substance, and that hereditary peculiarities can be as well 

 transmitted to the offspring by the former as by the latter. 



I can quite understand why a botanist should take this view, 

 and indeed, in bringing it forward, Professor Vines does not 

 stand alone. Waldeyer^ maintained, in 1888, that established 

 facts did not justify us in regarding the nuclear loops as 

 possessing an idioplastic nature. Among other zoologists, 

 Whitman ^ has pronounced very decidedly against the idio- 

 plastic nature of the nucleus, and in their recent work, Geddes 

 and Thomson ^ have done the same. 



The facts which suggested to my mind that the nuclear loops 

 are the material basis of heredity, — in fact the idioplasm, — are 

 enumerated in my fourth essay ^. They were chiefly the obser- 

 vations of Van Beneden on the process of fertilization in the 



1 ' Nature,' Oct. 1889, p. 623. 



'^ Waldeyer, ' Ueber Karyokinese und ihre Beziehung zu den Befruch- 

 tungsorganen,' Archiv fur Mikr. Anatomic, Bd. XXXII. 1888. 



^ Whitman, ' The Seat of formative and regenerative Energy,' Boston, 

 1888. 



^ Geddes and Thomson, ' The Evolution of Sex,' London, 1889. 



^ See Vol. I, p. 163. 



