ON DYSTERIA 473 



fact only the expression of a delicate membrane, which is bent so as 

 to have a ventral convexity, and connects together the two styles 

 (fig. 15). It might be said, therefore, that the posterior part of the 

 apparatus is a triangular membrane, deeply excavated in front, bent 

 so as to be convex downwards, and having its margins thickened and 

 produced into styliform enlargements. This curious piece of mechanism 

 is directed upwards and backwards, and terminates in the substance of 

 the body without any apparent connection with other parts. 



The whole apparatus is moveable. The posterior portion is pushed 

 against the anterior, and the heads of the styles come into contact 

 with the posterior convex edges of the supero-lateral pieces, and push 

 them forwards ; the posterior portion is then retracted, and the whole 

 apparatus returns to its previous arrangement. 



In one Dysteria, which had swallowed a filament of Oscillatoria, so 

 long, that the one extremity projected from the mouth, when the other 

 was as far back in the body as it could go, these movements took 

 place as many as twenty times in a minute. 



Mr. Dyster further informs me that, in one of these animals which 

 he saw feed the frond of Oscillatoria was rather " swum upon " than 

 seized, ingestion being accomplished by a smooth gliding motion, 

 apparently without displacement of the styles ; but that when the act 

 was completed the styles " gave a kind of snap and moved slightly 

 forwards." 



Mr. Dyster is inclined to think that the Oscillatoria passed through 

 the anterior ring-like portion of the apparatus. I have not seen the 

 animal feed, but on structural grounds I should rather have been 

 inclined to place the oral aperture at a, fig. 13, and to suppose that 

 the food would pass above the anterior ring. The apparatus is de- 

 stroyed by caustic potash, but remains unaltered on the addition 

 of acetic acid ; it is therefore, probably, entirely composed of animal 

 matter. 



Immediately above the annular portion of the apparatus, there is 

 invariably present a remarkable amethyst-coloured globule {f), ap- 

 parently composed of a homogeneous fluid. It has on an average a 

 diameter of t-oVo inch, and it is entirely lodged in the more convex 

 portion of the body.^ In many specimens no other colouring matter 

 than this can be detected, but in some, minute granules (tj^u inch) 

 ■of a similar colour are scattered through the body. What connection 

 these have with the large constant globule is not clear, since, although 



' In one or two specimens a minute amethystine globule, not more than one sixth the 

 -diameter of the large one, was visible immediately below and behind it. Acetic acid 

 'destroys the colouring matter. 



