450 FRANK R. LILLIE 
vations too numerous to mention demonstrate a very profound 
effect of the sperm nucleus on the egg cytoplasm, perhaps none 
more strikingly than Herlant’s (11) recent observations on the 
control of definite cytoplasmic areas (spermatic energids) by sper- 
matozoa in di- and tri-spermic eggs of the frog. 
Ziegler’s observations then indicate that the egg nucleus reacts 
to the egg cytoplasm when altered by the spermatozoén, but 
incompletely. It seems probable, therefore, that copulation of 
the germ nuclei also involves an interaction between them that 
completes the fertilization phenomena. It is interesting to note 
that, though the chromosomes form in Nereis from the egg nucleus 
after the spermatozo6n has been removed, they are not set free 
in the cytoplasm as they are after copulation with the sperm 
nucleus, but each is embedded in a matrix, and thus presents quite 
a different appearance from the normal. We may perhaps find in 
this fact, indicating lack of reaction between the chromatin and 
the cytoplasm, some evidence that the completion of fertiliza- 
tion involves interaction between the germ nuclei also. 
It remains to inquire briefly how this analysis compares with 
the analysis of fertilization given by experiments in artificial par- 
thenogenesis? In the first place we may note again that there is 
perfect agreement in the general fundamental distinction of two 
phases in the fertilization process as made first by Loeb, viz.: 
the cortical change which may be induced before penetration, 
and the internal changes, which follow penetration. As regards 
the cortical change, the view of Loeb (’09) that it is essentially 
a cytolytic change appears to me less fundamental than the view 
of R.S. Lillie (’11), that it is essentially an increase of permeabil- 
ity. One can readily understand that cytolysis should follow 
very rapidly on an increase of permeability induced by chemical 
means, which may be much greater than that normally induced 
by the spermatozoon, if such increase be not secondarily regulated. 
And in any event, if interchange between the egg and its medium 
be set up by increase of permeability, in a condition of inactivity 
of the nucleus, such as exists in the unfertilized egg, the resulting 
metabolism must be of a destructive character and so lead to a 
relatively rapid death of the egg as compared with eggs in which 
