OF THE PEOTOZOA. DYSTEKIA. 389 



the anterior ; and the heads of the styles come into contact A\ith 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 Oscillator'm 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 fui'ther informs me that in one of these animals which he 

 saw feed, the frond of OsciUatoria was rather ' swum upon ' than seized — 

 ingestion being accomjDlished 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 OsciUatoria 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 inchned to place 

 the oral aperture at, and to suppose that the food would pass above, the 

 anterior ring. The apparatus is destroyed by caustic potash, but remains 

 imaltered 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 inva- 

 riably present a remarkable amethyst-coloured globule, apparently composed 

 of a homogeneous fluid. It has on an average a diameter of ^^p^-jj in., and 

 it is entii'ely lodged in the more convex portion of the body. In many spe- 

 cimens no other colouring matter than this can be detected ; but in some, 

 minute granules (y^-^nro ^^0 ^^ ^ similar colour are scattered through the 

 body. AVhat connexion these have with the large constant globule is not 

 clear, since, although the dimensions of the latter vary from the size given 

 above to one-fom^th or less, no relation could be observed between this 

 diminution and the presence of the granules in other parts of the body. 



" Behind the amethystine globule, the substance of the body has the ap- 

 pearance, common to the Infusoria generally, of a mass of ' sarcode,' in 

 which the ingested matters are imbedded, and no clear evidence could be 

 obtained of the existence of any digestive ca\ity with distinct walls. 



" A little behind the middle of the body, and towards its ventral edge, 

 there is a clear spheroidal * contractile space/ which varies a good deal in 

 size. One measured ^ -\^^ th of an inch in diameter, and became entirely 

 obhterated in the contracted state. 



'' The contractions are not rhythmical, but take place iiTCgularly. On the 

 approach of death, the space becomes irregularly and enormously enlarged, 

 imtil it occupies perhaps a third of the whole contents of the body. 



" Immediately beyond the contractile space there is a curious oval body, 

 having its long axis ( - ^^^ ^^ in.) directed upwards, and containing a compara- 

 tively small central ca\ity, so that it appears like a thick- walled sac. 



*' Indications strongly suggestive of an inferior opening were sometimes 

 observed in this body ; but no demonstrative eridence of the existence of any 

 such aperture could be obtained. 



" The walls of the ventral groove are provided mth long and powerful 

 cHia — a remarkably strong one being attached behind the base of the 

 * appendage ; ' and by their means the animal, when free, is propelled at 

 no very rapid rate through the water. Its more usual habit, however, is 

 to remain fixed by means of the peculiar appendage ; and then the cilia act 

 merely in creating currents, by which nutritive matters are brought towards 

 the mouth. 



