THE BIOLOGY OF THE CELL SURFACE 



tonic sea-water develops without complete break-down of 

 ectoplasmic substance on the other, warns us against 

 attributing the cause of experimental parthenogenesis 

 directly to physical changes at the egg-surface, i.e., to 

 membrane-separation. 



Far from being an exception to be explained away, the 

 case of sea-urchins' eggs in responding to treatment with 

 the weak hypertonic sea-water without membrane-separa- 

 tion and with poor quality of development reveals clearly 

 what other eggs more sensitive in their ectoplasmic response 

 to experimental means do not: the ectoplasmic changes are 

 significant for the development in prospect. Again, as in 

 fertilization, we see that the quality of development depends 

 upon the quality of these initial ectoplasmic changes. 



They are violent eruptions which precede the evanescent 

 spinning that will accompany cleavages yet to come and 

 that will build gossamer-like tendrils to bind cell to cell. 

 Spermatozoon or parthenogenetic means. Nature's or exper- 

 imenter's, set the life of the egg in quicker motion; the 

 mitotic spindle comes and goes. The web of life gives a 

 pattern which we come to know as larval sea-urchin, worm 

 or clam. But almost with the moment that the egg's 

 vital activity moves at a quicker tempo we know through 

 the ectoplasmic behavior the quality of the events to come. 



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