REPRODUCTION 107 



too long the result would be the death of the 

 developing creature from sheer want of room, 

 so it must be released after the experiment has 

 gone a certain distance. What then happens ? 

 The egg goes on its way segmenting as if 

 nothing had occurred; there is no re-arrange- 

 ment of the nuclei, a most significant fact ; and 

 finally a perfectly normal larva of frog or sea- 

 urchin is the result. That is a frog or a 

 sea-urchin has been developed by means of a 

 series of events which one may safely say had 

 never occurred before, a tolerably clear proof 

 that there is^within the egg a power which is 

 able to steer it even through seas before unsailed 

 by any egg. 



A further development of this is to be studied Neresis 

 in experiments made by Wilson on the eggs of 

 Nereis, an annelid. It is a little difficult to 

 describe this experiment without becoming 

 highly technical, so that those who are familiar 

 with the real facts of the case must deal 

 leniently with the writer if he endeavours to 

 make the circumstances clear by simplifying 

 things to the utmost extent. In the normal 

 development of Nereis, then, it is known that 

 certain cells will develop into certain parts of 

 the later organism and others into different 

 and distinct parts. 



Now if the egg be allowed to develop under 



