202 O. P. Dellinger. 



iiess with which the method demonstrates the fibrillae of the axil 

 filament in the pseudopod of Actinosphaerium leads one to think that 

 this line of approach, or some modification of it, might yield valuable 

 evidence as to the structure of the neurite and axis cylinder of nerve 

 fibers. My observations on flagella and cilia as they pass under 

 different reagents from fibrillar to meshed or granular debris leads us 

 to conclusions as to the action of killing reagents on protoplasm differ- 

 ent from those arrived at by Fisher and Hardy. Instead of consider- 

 ing all fibrillar structures as artifacts, it would seem that few 

 investigators have divined the true fibrillar nature of protoplasm, 

 because they have used reagents that destroy or modify the fibrils. 



Alveoli exist in protoplasm, but reagents which preserve cilia 

 never yield completely alveolar structures that could possibly be 

 interpreted as Biitschli's "Schaume." The comparison of the alveolar 

 protoplasm of Actinosphaerium, or of any of Biitschli's Schaume, as 

 he figures them, with simple emulsions and with emulsions permeated 

 with delicate fibers, leaves little doubt that the alveoli of protoplasm 

 have their arrangement determined by fibrillae. This compromise 

 interpretation uniting the fibrillar and alveolar theories of the struc- 

 ture of protoplasm has been offered by other writers, and is rather a 

 matter for further investigation than for discussion in this paper. 



The resolution of the flagellum of Euglena, Chilomonas and 

 spirillum into four distinct fibrils and the demonstration of the 

 fibrillar structure of the cilia of Stylonj^chia leaves the way clear for 

 acceptance of not only the fibrillar theory of the structure of cilia, 

 but also i^or the conception of fibrillae as a component of any proto- 

 plasm. With its acceptance, all theories which regard cilia as tubes 

 or complex fluids appear gratuitous complications, and hence un- 

 tenable. 



In cilia or flagella capable of movement in all directions there 

 should be at least four contractile fibrils. I have succeeded in demon- 

 strating these in a typical series of forms. The presence of these 

 four fibrils not fused or cemented together, but coiled in a long spiral , 

 accounts for all their complex movements. Parker ('05) has pointed 

 out that in cilia incapable of reversing only one contractile filamert 

 is necessary, if this is attached to an elastic supporting rod. With 



