THE BIOLOGY OF THE CELL SURFACE 



Now although other organisms and their cells do not so 

 narrowly depend upon environmental changes, as do man 

 and other warm-blooded animals, nevertheless they quickly 

 respond to changes in their peculiar world, the environment 

 to which they are keyed and with which they are in accord. 

 For practical purpose, we abstract organisms and cells from 

 their surroundings — we could scarcely do otherwise in most 

 cases for we can not always study whole organisms or entire 

 cells at once but only their parts, each in turn. Still we 

 need ever to remember that we indulge in abstracting solely 

 for the purpose of comprehension and that an organism or 

 cell has a dependent relation to its environment. Life can 

 not exist apart from its external world. 



Nowhere, I think, in all biology does this most strong 

 relationship, unity, really, of organism or cell and environ- 

 ment more forcibly reveal itself than in the problem of 

 the parthenogenetic development of the animal egg. The 

 problem, how the egg can begin development through the 

 effect of some change in its environment, is to us still mys- 

 terious. The findings of experimental parthenogenesis 

 would help to dispel the mystery if they could serve to indi- 

 cate how environmental changes effect the initiation of 

 development in naturally parthenogenetic eggs. 



A plausible explanation is suggested by the fact that the 

 most commonly used means for inducing parthenogenesis 

 are simple changes in the medium, as changes in salinity, 

 acidity, and temperature. The normally parthenogenetic 

 egg probably differs from that which requires fertilization 

 in being more labile and more responsive; as such it would 

 react readily to one or another of these most commonly 

 occurring changes in the environment. That drying, radia- 

 tions, and puncture also induce development may be sig- 

 nificant. Certainly, they are environmental changes by 

 which experimental parthenogenesis can be induced. Since 

 we know these, we should seek to determine whether they 



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