258 PROTOPLASM 



particularly upon its granules, such as the so-called yolk granules 

 of the protoplasm of the ovum. Just as fine particles of iron 

 group themselves round the poles of a magnet in peculiar sys- 

 tems under the influence of its attraction, it was thought that 

 the attractive action of the centres of the rays took effect in some 

 way also upon the protoplasm and its particles. To such ideas 

 were inclined Fol (1873), myself (1874), Strassburger (1875), 0. 

 Hertwig (1875), and many later investigators, who cannot be 

 enumerated individually here. Auerbach, on the other hand, 

 had in 1874 expressed the view that the appearance of rays was 

 produced by the nuclear fluid streaming out into the protoplasm. 

 In 1876, when I brought forward my view, which I still uphold 

 even at the present time, and with much better grounds than 

 formerly, it was particularly pointed out that I could not, with 

 Auerbach, regard actual currents as the cause of the appearance 

 of radiations, but rather processes which we can now best denote 

 as migration of substances by diffusion. 



Anton Schneider, at a later date (1883), derived the radi- 

 ate appearances in like manner from the nuclear fluid. The 

 nucleus, which had become amreboid, " obtained the power of 

 sending out processes and rays" (p. 75). This was said to be 

 an " amo3boid property." It then follows from his further 

 description that Schneider also certainly regarded the nuclear 

 fluid as forming the rays. 



The idea that streamings in the interior of the protoplasm were 

 the cause of the appearance of rays was also maintained by Fol 

 (1879, pp. 251-256), and was especially based by him on the 

 accumulation at the clear central area?, as well as on the 

 growth of the pronuclei in fertilisation, and of the young 

 nuclei after division, in the same way as the opinion I had 

 already (1876) expressed upon the significance of these central 

 arese. Fol supposed that currents, in part centrifugal, in part 

 centripetal, produced the radiating appearances. But it was 

 not a question of nuclear fluid streaming outwards during these 

 processes, as Auerbach believed, but of currents of the proto- 

 plasm itself. In any case the phenomena were supposed not to 

 depend on an arrangement of the yolk granules, since the fila- 

 ments of protoplasm passing between the rows were much too 

 broad for that. His including me on this occasion among the 

 representatives of the hypothesis of attraction and polar orienta- 

 tion of the yolk molecules is an error to be regretted, since I had 

 refuted, as I have said, the hypothesis of attraction in 1876, and 

 had attempted an explanation which agreed with Fol's later one 

 in a series of essential points. The so-called central area?, or 

 attraction centres, as Fol terms them, he believes to be caused 



