MATERIALS FOR A MONOGRAPH OP THE ASCONS. 49d 



In "Clathriiia, sp. dub./' the densely packed granules 

 of the amoebocytes are of moderate size and glassy appearance, 

 without any particular tint (PI. 39, fig. 19, am. c.^), and the 

 nucleus is quite obscured by them. 



In blanca, cerebrum, and reticulum also the wandering 

 cells are colourless, but clearer than in the other species, and 

 of very compact form. The nuclei arc distinct. Of the three, 

 blanca has the least granular cells, reticulum the most 

 granular. 



In con tort a the granules are small and very numerous, of 

 rounded or oval shape, and the cells are often of very irregular 

 form (PI. 41, figs. 43, 44). 



Besides the granular and refringent amoebocytes just de- 

 scribed, there appear to be others constantly |)rei^cnt, which 

 have clear, finely granulated protoplasm. In coriacea (PI. 38, 

 fig. 10, am.C") the cells are found to vary very much in 

 size, but are distinguished by their nucleus, which has a very 

 distinct nucleolus, and is large in comparison to the cell body. 

 The cell itself is of irregular form, often with sharp processes. 

 In Clathrina, sp. dub., the clear wandering cells, so far as I 

 have studied them, are very similar to those of coriacea. 

 In contorta, on the other hand, these cells are similar 

 in their characters to the granular wandering cells, and only 

 differ in the minute size of their granules (PI. 41, figs. 

 46, 47). 



It is by no means certain that these cells are really different 

 from the granular cells. I am inclined to think that in the 

 case of contorta, at any rate, the clear cells are simply those 

 in which the supply of nutriment is exhausted. Perhaps they 

 correspond to the two classes of cells which Fiedler (1888) has 

 distinguished as " Fresszelleu" and '^ Nahrzellen." 



Finally, I have to mention very peculiar elements which I 

 have found in all the species. These are very minute cells with a 

 small faintly staining nucleus. Sometimes they are of globular 

 shape, but more often elongated, with the nucleus at one 

 extremity ; the former may be the condition of rest, the latter 

 that of active locomotion (PI. 39, figs. 17, 19, and PI. 41, fig. 41, 



