4 

 The Ectoplasm 



jt/aeckel,^ describing the cell-structure of 

 sponges, first used the terms, exoplasm and endoplasm. 

 He clearly distinguished two regions of the cytoplasm as 

 follows: 



In the hyaline contractile ground-substance of the proto- 

 plasm a varying mass of small dark granules is constantly 

 embedded; these usually surround the nucleus. On the 

 living flagellar cell, as long as it is active in situ, is a thin 

 granule-free cortical sheath. Thus one can more or less 

 clearly distinguish between a structureless outer cortical 

 substance and a granular inner medullary substance. The 

 outer cortical substance (exoplasma) is fully hyaline, some- 

 what firmer, less watery, more strongly refractive and 

 contains no granules; the inner medullary substance (endo- 

 plasma) is granular, somewhat softer, more watery, less 

 refractive (and contains the granules) and also now and 

 then vacuolar. No matter how distinctly the regions some- 

 times are set off from each other, they are never sharply 

 separated but pass insensibly the one into the other without 

 fixed limiting layer, much as is the case of hyaline cortex and 

 granular medullary substance in the body of an infusorian. 



Later Haeckel says^ that through its variously changing 

 surface formation, the exoplasm gives to the entire flagellar 

 cell its characteristic form. 



This clear description given by Haeckel may serve as the 

 basis of our definition of the ectoplasm (exoplasm of 

 Haeckel) : the ectoplasm is the superficial region of the 

 protoplasmic ground-substance set off from the remainder 



1 Haeckel, i8'/2. 

 ' Haeckel, I.e. 



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