THE STRUCTURE OF XENIA HICKSONI. 265 



granular structure. Its basal part, i. e. the part in continuity 

 with the vacuolated portion of the cell, stains deeply with 

 haematoxylin, and in most cases shows very faint longitudinal 

 striations which are visible only in the proximal third of the 

 process. 



The processes usually taper towards their free end, but in 

 one instance this end is slightly broadened and flattened 

 (fig. 25, A). In one case the process, which is a very large 

 one, bears a short branch near the middle of its length 

 (fig. 25, B). This is the only branched process found among 

 many hundreds examined. The processes of most of the cells 

 project outwards almost at right angles to the free surface of 

 the endoderm (figs. 20, 21, 23, 24), but there are many similar 

 to the one drawn in fig. 22, in which the process is strongly 

 curved and apparently moderately flexible. 



These curious processes are very numerous, and are found in 

 all parts of the endoderm lining the coelenteron and tentacles, 

 but are most abundant in the portion of the coelenteron 

 situated in the body of the polyp and in the upper part of the 

 stem (PI. 25, fig. 9). 



The nature of these processes is difficult to determine. In 

 the preliminary note to the Royal Society (1898, written in 

 February) I called them pseudopodia, but further investigation 

 shows that the word flag el la would probably better express 

 their nature. The processes appear to be permanent, to have 

 a moderately definite shape gradually tapering from base to 

 tip, and to be flexible. The word pseudopodia implies more 

 temporai'y structures with many diff"erent and continually 

 changing shapes, while the term flagella implies tapering whip- 

 lash-like processes of more permanent and definite shape. The 

 homogeneous structure of the greater portion of these pro- 

 cesses, differing so markedly from the vacuolated granular 

 protoplasm of the rest of the cell, is also more in accord with 

 their being flagella, as pseudopodia have the same structure as 

 the body of the cell from which they are protruded. 



It is difficult to suggest the probable function of these giant 

 flagella. They are evidently motile organs, as they may be 



