CELL-LIFE AND CELL-MULTIPLICATION. 253 



became manifest that within these minute structures pro- 

 cesses and products of an astonishing nature are to be seen. 

 These we have now to contemplate. 



In the passages just referred to it was said that the ex- 

 ternal layer or cell-wall is a non-essential, inanimate part pro- 

 duced by the animate contents. Itself a product of proto- 

 plasmic action, it takes no part in protoplasmic changes, and 

 may therefore here be ignored. 



74&. One of the complexities within complexities was 

 disclosed when it was found that the protoplasm itself has a 

 complicated structure. Different observers have described it 

 as constituted by a network or reticulum, a sponge-work, a 

 foam-work. Of these the first may be rejected; since it 

 implies a structure lying in one plane. If we accept the 

 second we have to conceive the threads of protoplasm, corre- 

 sponding to the fibres of the sponge, as leaving interstices 

 filled either with liquid or solid. They cannot be filled with 

 a continuous solid, since all motion of the protoplasm would 

 be negatived; and that their content is not liquid seems 

 shown by the fact that its parts move about under the form 

 of granules or microsomes. But the conception of moving 

 granules implies the conception of immersion in a liquid or 

 semi-liquid substance in which they move not a sponge- 

 work of threads but a foam-work, consisting everywhere of 

 septa interposed among the granules. This is the hypothesis 

 which sundry microscopists espouse, and which seems me- 

 chanically the most feasible: the only one which consists 

 with the " streaming " of protoplasm. Ordinarily the name 

 protoplasm is applied to the aggregate mass the semi-liquid, 

 hyaline substance and the granules or microsomes it con- 

 tains. 



What these granules or microsomes are whether, as some 

 have contended, they are the essential living elements of the 

 protoplasm, or whether, as is otherwise held, they are nutri- 

 tive particles, is at present undecided. But the fact, alleged 



