Maturation of the Egg 247 



such as an acid must be formed before the one or more enzymes 

 necessary for development can be activated, we can under- 

 stand that the absence of this substance must lead to a pause in 

 the life-cycle of the organism. The introduction of this sub- 

 stance from without, or the initiation of its production within, 

 the cell will then effect development. 



It may be well to remember also in this connection that 

 the unfertilized eggs of purpuratus can be induced by a hy- 

 pertonic solution to segment into two or four cells, without 

 developing further. They go into a resting stage again, from 

 which they can be aroused by causing artificial membrane 

 formation. It would be very important to know why these 

 eggs did not go on developing after they had started to 

 segment under the influence of the treatment with a hyper- 

 tonic solution. 



3. It appears to be very generally the case that maturation 

 can be induced by treating eggs in the oocyte stage with sodium 

 hydrate; for I have obtained results similar to those recorded 

 for Polynoe, with the eggs of Nereis, and also of Sipunculus. 

 Unripe eggs which refused to mature in sea-water did mature 

 when exposed for a few hours to hyperalkaline sea-water at 15° C. 

 With regard to the maturation of the eggs of Nereis at Pacific 

 Grove, I made an observation that may perhaps be important 

 from the point of view of the mechanism of maturation and 

 membrane formation. In the immature egg of Nereis there 

 is a greenish-blue pigment distributed evenly over the entire 

 surface. This pigment layer contains many small, highly re- 

 fracting droplets which may be fat particles. On treating 

 the eggs with hyperalkaline sea-water, so that they mature, 

 the following changes are observed : first, a membrane is Ufted 

 up, comparable to the fertilization membrane of the sea-urchin 

 egg; second — ^but long after membrane formation — the numer- 

 ous droplets (fat?) flow together into a few large drops; third, 

 the greenish mass, which had previously formed an even layer 



