THE FUNCTION OF NBTTLEGELLS. 393 



The Function of Nettlecells. 

 By 



R. von liendenfeld, Pli.D., F.Ii.S., 



Assistant in the Zoological Laboratory of University College, London. 



With Plate XXX, fig. 4. 



Morphology. 



Both in the ectoderm and the entoderm of all Polypomedusas 

 these elements are met with. They are never absent in the 

 ectoderm in any species, and are generally also found in the 

 entoderm. 



Their structure has been investigated by numerous authors ; 

 particularly F. E. Schulze (1), O. Hamann (2), Korotneflf (3), 

 and the author (4) have studied their structure and action 

 more closely. Also Jickeli (5) has dwelt on this subject. 



However different the animals may be on which these Nettle- 

 cells are found, the latter nevertheless are always of the same 

 structure, although they may vary very much in size. The 

 large ones are fewer in number and more determinate in their 

 position than the small ones. No Nettlecells of the large kind 

 are found in the entoderm. 



The Nettlecells, or, as Schulze calls them, cnidoblasts, consist 

 of a cell the greater portion of which is occupied by the well- 

 known highly refracting vesicle, on the size of which the 

 size of the whole cnidoblast depends. The granular proto- 

 plasmatic portion of the Nettlecell is reduced in bulk so much 

 that it only forms a thin coating over the surface of the vesicle. 

 In one locality this plasmatic coat is slightly thickened, and here 

 the flattened nucleus, closely attached to the vesicle, is situated. 



