B. Investigations on Protoplasmic Structures 



In the description of the drops of foam, I have intentionally- 

 avoided entering into what was the starting-point of my 

 experiments, namely, the imitation and possible explanation 

 of protoplasmic structures. In proceeding to this,*! may 

 first point ovit the really striking resemblance to protoplasm 

 which is presented by successfully prepared drops of foam, 

 when they have been cleared up in glycerme and are suffi- 

 ciently compressed. Since the refractive index of their oily 

 framework is greater, even after being cleared in glycerine, 

 than that of the framework of living protoplasm, the impres- 

 sion made by the foam approximates more to that given by 

 protoplasm which has been killed and fixed. I have often 

 placed preparations of the foam before some of my colleagues, 

 who were themselves not inexperienced in the investigation 

 of protoplasmic structures, and were quite unbiassed in their 

 opinions, and asked them what they believed the object to 

 be which they were shown, and of the nature of which they 

 were quite ignorant. One of them guessed it to be an egg. 

 cell, another thought it was Ehizopod protoplasm, or 

 something of the sort, v Although the pictorial method of 

 representation does not fully succeed in reproducing the 

 impression made by the natural object, yet the close resem- 

 blance may be convincingly proved by a comparison of the 

 photographs of drops of foam, which supplement this work, 

 with those of the protoplasm of various cells, among which 

 I would especially draw attention to the photographs of 

 ganglion cells from Zumhricus (XIII.) and of ^thalium 

 septiciim (XV., XVII.) 



Although it was not part of my original intention to 



