424 



EVENINGS AT THE MICKOSCOPE. 



up in some instances with an approach to regularity, 

 but much more commonly in loose contortions, like an 

 end of thread rudely rolled into a bundle with the 

 fingers. 



" The armature of this kind does not diifer essen- 

 tially from that already described. It is true, I have 

 detected it only in Corynactis, where the short ectho- 

 rcBum of the Tangled Cuida is surroxmded throughout 

 its length by a barbed strebla of three bands. The barbs 

 are visible, under very favourable conditions for obser- 

 vation, even while the tangled wire remains enclosed 

 in the cnida, but their optical expression is that of ser- 

 ratures of the walls, without the least appearance of a 

 screw. This, I say, is the only species in which I have 

 actually seen the armature of the eothorceum in this kind 

 of cnidcB, but I infer its existence 

 from analogy in other species, where 

 the conditions that can be recognis- 

 ed agree with those in this, though 

 the excessive attenuation of the 

 parts precludes actual observation 

 of the structure in question. 



" Spiral Cnidse constitute the 

 third form. In a few species, as 

 SagarUa parasitica, Tealia crassi- 

 Gornis, and Gerianihus memhra/na- 

 ceus, I have found very elongated 

 fusiform cnidm, which seem com- 

 posed of a slender cylindrical thread, 

 coiled into a very close and regular 

 spiral. In some cases the extrem- 

 ities are obtuse, but in others, as in T. crassicornis [an 

 example of which I now show you] the posterior ex- 



CNIDA OP COETNAOnS. 



