On the structure of ero ss -striated muscle. 183 



universal and an essential element in the structure of living substance. 

 Prima facie, it seems, at the least, improbable that the gliding proto- 

 plasm of the vegetable cell, of the Ehizopod pseudopodium, of the white 

 blood corpuscle, freely carrying along with it in its rapid streaming 

 movements, solid granules even of large size, should have such a pre- 

 formed structure as this theory supposes. We should have to assume 

 a constant breaking down and re-formation of the structure with every 

 movement of a granule, and the terms „structure" and „preformed 

 network" become either simply unmeaning or even misleading terms. 

 Nevertheless, if such a structure does really exist in actively contract- 

 ile cell-protoplasm, these difficulties of comprehension must be either 

 got over, or left untackled until our knowledge of the physics of the 

 cell substance has become more extended. But can the reticulum 

 really be proved to be a constant element in amoeboid protoplasm? 



So far as I am aware no evidence has been offered to show that 

 such actively motile protoplasm as that which lines the cells of Val- 

 lisneria or forms the ectoplasm of Amoeba, or the pseudopodia of the 

 white blood corpuscle does actually possess the structure which is 

 considered essential to the living substance of the cell by many cyto- 

 logists of the present day. I have, however, thought it well to test 

 the question by a careful investigation of such protoplasm, examined 

 both during life and after fixation in the living condition. With this 

 object I have selected, as being the most readily available and of 

 sufficient dimensions for the purpose, the white blood corpuscles of the 

 newt (Triton cristatus). These, in preparations of blood made either 

 without addition of other fluid, or with the addition of a small quantity 

 of salt solution only, I have most carefully observed with a Zeiss's 

 apochromatic oil immersion of 1,30 aperture and 2 mm. focal distance, 

 with compensating oculars from 4 to 12, giving an ultimate magni- 

 fication of about 1500 diameters. Although the corpuscles soon become 

 spread out on the coverglass and their thinned out pseudopodia are 

 in the most favourable condition for observation, I have not been 

 able to detect in these processes a trace of reticular appearance. The 

 main part or the body of the cell, situate around the nucleus, has 

 frequently, apart from the conspicuous granules which characterize 



