HELIOZOA 93 



meshes at about O'OOIO mm. The figure shows, however, 

 that meshes also occur of much smaller diameter. 



Earlier observers have already found that the most 

 superficial zone of the intracapsular protoplasm, bordering on 

 the wall of the central capsule, is distinctly radially striated. 

 In the sections investigated this striation was also very 

 distinct, and at the same time it could be demonstrated 

 with certainty that it only depended on the arrangement of 

 the meshes in radiating series. This is plainly shown by 

 Fig. 2, b, which represents the striated protoplasm bordering 

 on the periphery of a large vacuole. 



Heliozoa 



As far back as 1885 I reported that the protoplasm of 

 the large Actinosphccrium exhibits the finely meshed struc- 

 ture well, after treatment with chrom-osmic-acetic acid, and 

 that in the pseudopodia also the same structure is plainly 

 recognisable. More recently I have found an opportunity of 

 investigating this form, as well as ActinopJirys sol. In both, 

 with the optical apparatus that is now obtainable, I was 

 able to convince myself easily as to the meshed structure 

 of the endoplasm in the living condition, and also to 

 observe the radiate layer of meshes distinctly present 

 round the food vacuoles of Actinophrys. The protoplasm of 

 the pseudopodia of Actinophrys appeared in part composed 

 of distinct longitudinal fibres. Moreover, this fibrillar 

 modification of the protoplasm could be followed through the 

 coarsely vesicular ectoplasm into the finely meshed endo- 

 plasm, and at the same time it could be demonstrated that 

 the fibrous tracts pass into the mesh work of the endoplasm. 



In Actinosplmrium also the meshed structure of the 

 protoplasm of the pseudopodia could be made out even 

 in the living condition (see Plate X. Fig. 3). To do so is 

 naturally somewhat difficult on account of the continual 

 streaming movements. Since, however, the meshed appear- 

 ance shown by the protoplasm of the living pesudopodia is 

 in no way altered by killing with picro-sulphuric-osmic 

 acid, but only becomes sharper and plainer, this proves, as 



