354 ELEMENTARY BIOLOGY. [CHAP. 



(Sect. 5. d. P) ; one or more of these may be con- 

 nected with an individual cell. They arise as out- 

 growths of the constricted cell-base, the whole fre- 

 quently having the appearance of an inverted T with 

 a thick stem (cell-body) and greatly elongated arms 

 (the fibres). 



d. The ce//s of the interstitial tissue (cf. Sect. 5. ^. )8) much 

 smaller than a^ and often separable from one another 

 only with difficulty. Numbers of them will be found 

 to contain two nuclei (evidence of active division). 



c. The nematocysts ; highly refractive bodies to be found 

 in both a and d — in the latter in abundance and in 

 all stages of development. Look for the under- 

 mentioned (cf Sect. 3). 



a. The larger ?tematocysts ; each consists of a body^ 

 ovoidal and truncated, with a strongly-marked 

 double contour due to the thickness of its wall : a 

 neck^ inverted and beset by three or four powerful 

 spines; a filament^ lying within the base of the 

 body, coiled into a spiral the edges of which may 

 occasionally be seen (cf. Sect. 3). ^ 



Compare a large nematocyst in the everted state ; 

 the summit of the neck is beset by a series of ex- 

 cessively delicate spines. 



I 



p. The smaller nematocysts ; rarely present in the larger* 

 cells. Each is ovoidal and much smaller than a, 

 having a similar double contour. The filament ; 

 but |- to Y2- the length of, and very much stouter 

 than, that of a; at rest looped, in eversion fre- 

 quently spiral (cf. Sect. 3). 



