THE PRESENT POSITION OF CELL-THEORY. 229 



convinced of the close analogy in structure between the 

 artifact and the natural product. The resemblance between 

 the two is exact, and it is astonishing. The optical char- 

 acters of the artificial product are explained, on physical 

 grounds, as the outcome of a certain structure, namely, an 

 alveolar structure. The identical optical characters of pro- 

 toplasm may surely be explained on the same grounds. It 

 is not pushing analogy too far to say that identical optical 

 characters are the result of identity of structure. The 

 analogy is somewhat strained when it is sought to prove 

 that the identity of the streaming movements in the arti- 

 ficial product with those in protoplasm are attributable to 

 the same physical causes. The chemical constitution of 

 the. two bodies is so different that the phenomena observed 

 might be regarded as secondary. Nor is the identity 

 absolute, for Biitschli himself points out that the induced 

 currents in the surrounding medium take place in the re- 

 verse sense in an amoeba to what they do in the case of 

 the microscopic foam. I cannot think that the criticism of O. 

 Hertwig invalidates Biitschli's theory seriously. Hertwig 

 says that lamellae of oil consist of a fluid which is not 

 miscible with water. If the comparison between the 

 structure of an emulsion and the structure of protoplasm 

 depends on something more than a superficial resemblance, 

 then the lamellae of plasma which are compared with the 

 lamellae of oil must consist of a solution of albumen 

 or of a fluid albumen. But a solution of albumen is 

 miscible with water, and therefore it would mix with the 

 contents of the alveoli : emulsions of albumen must be formed 

 with air, not with water. To this Biitschli answered that 

 the framework of plasma consists of a fluid composed of a 

 combination of an albumen and a fatty acid, which was 

 therefore not miscible in water. Another obvious answer 

 is that living plasma is not a simple albuminous solution, 

 for if it were most protozoa could not exist, they would 

 immediately dissolve in the water in which they live. 

 Whether a fatty acid exists in combination with the plasma 

 or not, there is something in the constitution of living- 

 plasma which differentiates it from albumen, for it does not 



