224 THE CONTINUITY OF THE GERM-PLASM AS THE 



pretation. In former times it could only be regarded as of purely 

 phyletic significance : it could only be looked upon as the last remnant 

 of a process which formerly possessed some meaning, but which is 

 now devoid of any physiological importance. We are indeed com- 

 pelled to admit that a process does occur in connexion with the true 

 polar bodies of animal eggs, which we cannot explain on physio- 

 logical grounds ; I mean the division of the polar bodies after they 

 have been expelled from the egg. In many animals the two polar 

 bodies divide again after their expulsion, so as to form four bodies, 

 which distinctly possess the structure of cells, as Trinchese observed 

 in the case of gastropods. But, in the first place, this second division 

 does not always take place, and, secondly, it is very improbable 

 that a process which occurs during the first stage of ontogeny, 

 or more properly speaking, before the commencement of ontogeny, 

 and which is, therefore, a remnant of some excessively ancient 

 phyletic stage, would have been retained up to the present day 

 unless it possessed some very important physiological significance. 

 We may safely maintain that it would have disappeared long ago 

 if it had been without any physiological importance. Relying 

 on our knowledge of the slow and gradual, although certain, dis- 

 appearance, in the course of phylogeny, of organs which have lost 

 their functions, and of processes which have become meaningless, 

 we are compelled to regard the process of the formation of polar 

 bodies as of high physiological importance. But this view does 

 not exclude the possibility that the process possessed a morpho- 

 logical meaning also, and I believe that we are quite justified in 

 attempting (as Biitschli 1 has recently done) to discover what this 

 morphological meaning may have been. 



Should it be finally proved that the expulsion of polar bodies 

 is nothing more than the removal of histogenetic nucleopl:ism 

 from the germ-cell, the opinion (which is so intimately connected 

 with the theory of the continuity of the germ-plasm) that a re- 

 transformation of specialised idioplasm into germ-plasm cannot 

 occur, would be still further confirmed ; for we do not find that any 

 part of an organism is thrown away simply because it is useless : 

 organs that have lost their functions are re-absorbed, and their 

 material is thus employed to assist in building up the organism. 



1 Biitschli, 'Geclanken iiber die morphologische Becleutnng der sogenannten Rich- 

 tungskcirperohen,' Biolog. Centralblatt, Bd. VI. p. 5, 1884. 



