VAN BENEDENCARNOY 173 



he even ascribes to the cilia a composition of both kinds of 

 protoplasm. 



Since we shall frequently have to discuss L^ydig's views 

 again later on, this short exposition of his opinionwill suffice 

 for the present. 



E. van Beneden, in his investigation of the protoplasmic ^ 

 structure of ova, etc., of Ascaris, was at first, at any rate, on 

 what is in my opinion the right tack, since he was inclined 

 to refer the net-like structure of the protoplasm to the exist- 1 

 ence of numerous vacuoles, and pointed to Actinosphcerium 

 and similar forms for comparison (p. 82). But he was 

 doubtful whether the vacuoles which produced the reticular 

 structure were entirely shut off from one another. In the 

 further course of his work, however, this view was with- 

 drawn altogether, and in its place another appeared, which 

 seems to have been put forward as the result of the study 

 of the interesting structure of the spermatozoa. Here, as in 

 the general part dealing with protoplasmic structures, van 

 Beneden consistently terms the fibril the structural element 

 of protoplasm. The protoplasm is said to consist of nodular^ 

 fibrils and an intervening substance. The fibrils are 

 orientated in the three directions of space, and their nodal 

 points, which represent actual thickenings, are connected 

 by finer fibrillffi. In this way there results a " protoplasmic 

 trellis work" (treillage). The fibrils are contractile, and 

 hence the framework is capable of alteration. It would 

 appear doubtful whether the intervening matrix is identical 

 with the contents of the larger vacuoles ; if this is the case, 

 a special wall with extremely narrowed meshes must be 

 formed round the vacuole, just as Heitzmann and Schmitz 

 had already assumed. 



Pfitzner, in 1880, when giving an account of the epi- 

 thelial cells of the salamander larva, described a meshwork 

 in the protoplasm which at the surface of the cell passed 

 distinctly into the radially striated border; and in 1883 he 

 gave a good description of the reticular structure of the red 

 blood corpuscles of Amphibia, publishing later (1886) a 

 most excellent figure. At the same time he developed his 

 theoretical views as to the origin of such structures, which 



