THE CELL ASTER 489 



of which are either so thin as to be invisible or possess a refractive 

 index similar to that of the surrounding substance ('02, p, 217). 



Regarding the gross structure of protoplasm, Biitschli's inter- 

 pretation of an alveolar structure is true only for special cases 

 where the microscopic appearance of a meshwork is due to the 

 inclusion in the hyaloplasm of droplets or granules which are 

 not fundamental to protoplasm (Mathews, '07, Kite, '13, Cham- 

 bers, '17). In killed protoplasm the visible meshwork is dis- 

 tinctly a coagulation phenomenon and has nothing to do with 

 the structure of li\'ing protoplasm (Chambers, '17). Biitschli's 

 interpretation applies rather to protoplasm in connection with 

 its ultra-microscopic, colloidal structure and even then probably 

 only to its gelled or coagulated condition. 



The protoplasm of certain marine ova (Asterias, Arbacia, 

 Echinarachnius, Cerebratulus) has been described in a recent 

 paper (Chambers, '17 a). It consists of a hyaloplasm in which 

 clear more or less spherical bodies of 2 to 4 micra in diameter, 

 the macrosomes, and very small granules, the microsomes, are 

 crowded together. The hyaloplasm of the resting egg is in the 

 sol state and is of such a slight viscosity that the nucleus and 

 cell granules can be readily rolled and pushed about in it by the 

 needle. At the egg surface the hyaloplasm is in the gel state and 

 there seems to be no doubt that protoplasm owes its high vis- 

 cosity, extensibility and contractility to the gelatinized con- 

 dition of its surface film. 



In experiments which involve tearing of protoplasm one must 

 recognize a limit to the amount and character of the mechanical 

 disturbance which the general protoplasm can bear without 

 disorganization. Considerable displacement without injury to 

 the protoplasm can be produced by a slow even movement of the 

 needle. If, however, the movement be quick and rapidly re- 

 peated, disorganization with a change to a decidedly acid re- 

 action occurs accompanied either by a liquefaction or an irre- 

 versible coagulation of the disorganized protoplasm. 



