Xo. 40(5] 



NOTES AND LITERATURE 



285 



The division of the eentrosomes, the formation of the astro- 

 sphaeres, the division of the chromosomes and of the cytoplasm, 

 are not to be considered, according to Pr/ibranrs summing up. 

 as constituting a series of causally connected events, but are the 

 result of the same primary cause. While this poinl of view is sym- 

 pathetic to the reviewer also, it should be clearly understood that 

 we entirely lack sufficient evidence to establish such an attractive 

 interpretation. Even if all these changes are the result of one 

 cause, we can form no conception of what that cause may be. 

 Our author's conclusion, at the end of the next chapter, to the 

 effect that this common cause is to be found in a system of 

 surface tensions, can scarcely be said to be at present more than 

 the working hypothesis of a few thinkers of the school of devel- 

 opmental mechanics. One does not have to look very far for 

 facts that are difficult to explain on such a view. 



It is pointed out at the end of chapter VI. that the arrange- 

 ment of the bhistomeres conforms to Plateau's law of minimal 

 surfaces. While it is true that such a Law may appear to ac- 

 count for cell arrangement, we should not overlook the fact that 

 a similar arrangement follows if the cells are simply flattened 

 against each other by pressure from outside. Possibly also 



gastrulation is the outcome of chemotactic action, i. e., of an 



attempts to interpret the results in the following way. Different 

 chemical stuffs are supposed to be present in different zones of 



