ACTION OF THE SPERMATOZOON UPON THE EGG 235 
Finally, the rate of segmentation is the same in the eggs 
developing parthenogenetically as in eggs fertilized by sperm. 
This also proves that the sperm does not induce development 
by any catalytic influence, but by the removal of an obstacle 
or an inhibiting factor which obviously exists in the condition 
of the cortical layer. Formerly the writer had suggested that 
the removal of this obstacle consisted in the secretion of an 
inhibitive substance from the egg,! a view which Bataillon? 
and Lillie’ have since adopted; but the fact that complete 
cytolysis of the unfertilized sea-urchin egg by saponin raises 
the rate of oxidations in the same way as membrane formation 
or fertilization suggests that the cytolysis of the cortical layer 
is the essential removal of the ‘obstacle.’ 
The destruction of this cortical layer, the artificial membrane 
formation, leads to a rapid increase in the rate of oxidations 
in the egg of the sea-urchin. These oxidations form the foun- 
dation of all the further cytological changes in the egg, since 
their -suppression inhibits these cytological changes. It is, 
therefore, obvious that the point which demands further ex- 
planation is the connection between membrane formation or 
cytolysis and rate of oxidation. It is conceivable that the cor- 
tical layer of the unfertilized egg forms a crust impermeable 
to oxygen, but there is no proof for such an assumption. It 
is also conceivable that there is present in the surface of the 
egg a substance which inhibits the development of the egg, and 
that this substance is altered or removed in the process of 
membrane formation. It is finally conceivable that the surface 
1 Loeb, University of California Publications, Physiology, II, 1905. 
2 Bataillon, ‘‘Le probléme de la fécondation circonscrit par l’imprégnation 
sans amphionyxie et la parthénogénése traumatique,’’ Arch. de Zool. expér. et 
gén., XLVI, 101, 1910. 
3 Ff. Lillie, Jour. Morphol., XXII, 361, 1911. 
4 There is a possibility that the egg contains in the cortical layer a catalyzer 
or substances causing an increase in the rate of chemical reactions in the egg. 
While in the unfertilized eggs these substances are not able to act, they are rendered 
available if the cortical layer is cytolyzed. This possibility was set forth by me in 
Proc. Soc. for Exper. Biol. and Med., VII, No. 4, April 20, 1910. 
