No. 503] 



NOTES AND LITERATURE 



757 



analysis of the experimental facts indicate that in Crustacea 

 there is no color vision. But in the short period since her ac- 

 count was written. ~M inkiewiez has domonst rated experimentally 

 a refined color vision in this group, the animals standing with 

 much success the test of "matching colors" for their disguises. 

 If in so comparatively simple a matter the negative indications 

 were wrong, how much dependence can be placed on our now 

 having a complete knowledge of what exists in higher spheres? 

 Every experimenter knows how near he came to missing some 

 important result that lie finally reached; he realizes that there 

 are doubtless many things equally important that he did miss. 

 The positive results of experimental science are stones for build- 

 ing; the negative ones are often merely space as yet unfilled. 

 Yet such summaries as .Miss "Washburn gives us of the knowledge 

 at any particular time are necessary and valuable, especially 

 when, as in the present case, they are put together by one fully 

 conscious of the limitations of the subject, 



Zur Strasseir in his lecture before the (ierman Congress of 

 Naturalists and Physicians deals with another aspect of mind 

 in animals; with a question of the greatest practical interest to 

 experimentalists, and of great theoretical inlerest to all. Are 

 "psychic factors** required for explaining the behavior of ani- 

 mals, or can we explain the behavior throughout from the ex- 

 perimentally perceivable, objective, factors; can animals be un- 

 derstood as physico-chemical machines.' Zur Strassen follows 

 a course of reasoning which is often begun, but which usually 

 stops in the middle; the author carries it to the end. with illu- 



As his guide he takes the principle of parsimony in its widest 

 sense — that we shall not assume the existence of any factor which 

 is not required in order to explain the results. A further prin- 

 ciple, acted upon but not set forth in words, is that mere in- 

 crease of complication, no matter how great, does not in itself 

 imply a new principle of action. Cnder these principles he 



