ORIGIN AND DEVELOPMENT 53 



ments in microscopes and in the methods of 

 microscopy, structure has been rendered 

 apparent where it was not supposed to exist. 

 Physicists had endeavoured to fix physiolo- 

 gists on the horns of a dilemma. Either an 

 ovum must have structure, which physiologists 

 at one time doubted, otherwise complicated 

 structures must have been evolved out of 

 what was structureless (which is inconceivable) 

 or, if the physiologists admit the existence 

 of structure, then the minute cubical capacity 

 of the fecundated ovum could not contain all 

 the organic molecules necessary to account 

 for the transmission of hereditary characteris- 

 tics. Since this criticism was made, in the 

 first place, structure in a fecundated ovum has 

 been admitted, and, in the second, we now have 

 more accurate estimates of the size of atoms 

 and molecules than was then available, with 

 the result that, even in the minute cubical 

 mass of a fecundated ovum, there is room 

 enough for all the molecules necessary to 

 transmit, by their combinations, all that is 

 required to account for even minute character- 

 istics in offspring. Further, the new physical 



