94 PROTOPLASM 



it seems to me, that the pseudopodia killed in this manner 

 show the normal structure. At the base of the pseudo- 

 podia the layer of protoplasm surrounding the axial thread 

 is several meshes in thickness, and diminishes to a single 

 layer of meshes towards the ends. For the rest, I have 

 not yet investigated more closely how the matter stands 

 with the finely attenuated external ends of the pseudopodia. 

 On killing with picro-sulphuric-osmic acid the protoplasm 

 of the pseudopodia frequently contracts itself up into 

 varicose swellings along the axial thread, as a result of 

 which the latter becomes quite denuded in places (see Plate 

 XII. Fig 1). 



In the ectoplasm of the living Actinosphasrium I could 

 observe the meshed structure only very indistinctly, when 

 the surface of the large vacuoles was focussed. It appeared 

 most distinct in the obliquely sloping walls of the external 

 marginal vacuoles. 



After treatment, however, with the osmic mixture 

 already mentioned, the meshed structure is everywhere easily 

 recognisable in the ectoplasm. Whether or not the ultimate 

 structure of the axial thread was similar, was a point 

 not successfully determined, though it occasionally appeared 

 to be so. 



Marine Rhizopoda with Calcareous Shells and Reticulate 

 Pseudopodia 



While staying at the Zoological Station at Naples in the 

 beginning of the year 1890, 1 had an opportunity of devoting 

 some study to the above-named Ehizopoda. As objects of 

 investigation use was made of representatives of the genera 

 Discorbina, Planorbulina^olystomella, Cornuspira, and various 

 Miliolidce. I directed my attention principally to the 

 pseudopodia, but also investigated to some extent the proto- 

 plasm enclosed by the shell. 



I will commence with the latter. If one of the Ehizo- 

 pods mentioned be burst by means of pressure, or broken 

 up with fine needles, it is easy to convince oneself that the 



