No. 2.] ORGANIZATION OF THE EGG OF UNIO. 26 1 



time back and forth across the line of equilibrium. Even after 

 this the spindle may be carried around more or less by stream- 

 ing of the protoplasm, and yet it comes to rest for the division 

 in a definite place ; but it may be that the random streaming 

 has become converted into a slow, directive movement that 

 determines the position of the spindle. This viust be the case, 

 if the theory is to apply here. The theory would seem to 

 imply that protoplasmic currents may be adapted to purposes 

 of differentiation, not that all streaming is definitely directed ; 

 just as cell division may be adapted to purposes of differ- 

 entiation, though it may equally be without definite refer- 

 ence to it. 



VII. Organization of the Egg. 



We have been assured frequently of late by Driesch {e.g., '99, 

 p. 717) that descriptive investigations can at most yield nega- 

 tive results, that only experimental results justify general 

 theorizing. While I would personally agree with Driesch that 

 such theorizing as he sometimes indulges in cries aloud for 

 justification, I do not find anything in his remarks to cause 

 descriptive writers the slightest qualms in drawing conclusions 

 from their observations. "Negative" and "positive" are 

 purely relative terms, and as the scientific method at present 

 universally followed consists in testing working hypotheses by 

 all means available, I cannot see why a fact of pure observation 

 should be " negative " in a different sense from one based on 

 experiment ; or less instructive, especially in biology, where 

 most of the conditions are unknown, and the experimenter is 

 generally unaware of much that he has modified. I should be 

 the last one to deny the value of the results reached in the 

 field of experimental embryology, in which Driesch has done 

 such brilliant work; but surely it is time to object when 

 this writer claims monopoly of the faculty of judgment for 

 those who have shaken eggs. Rather in our speculation 

 should we check our observations with experiment and our 

 experiments with further observation, for only one thing is 

 more deadly than a careless observation, and that is a doubtful 

 experiment, and either may lead astray. Surely one who has 



