182 Voracity of the Asplanchna, and its Stomach Currents. 



VORACITY OF THE ASPLANCHNA, AND ITS 

 STOMACH CURRENTS. 



BY HENRY J. SLACK, F.G.S., 

 Member of the Microscopical Society of London. 



The ordinary text-books do not contain a satisfactory portrait 

 of one of the most interesting rotifers, the Asplanchna 

 JBrightwellii, and the peculiar arrangement and mobility of the 

 various parts render it almost impossible that a striking like- 

 ness should be produced.* In two successive seasons I obtained 

 these creatures from Hampstead Heath, and last November and 

 December found them fairly plentiful in one or two very small 

 ponds at the back of the Castle Tavern. When a fortunate dip is 

 made, and the bottle held up to the light, little exquisitely 

 transparent glassy bags will be seen swimming about, and they 

 will be made noticeable, less by their extremely delicate outline 

 than by a solid-looking patch of coloured matter, generally 

 golden yellow, which stimulates curiosity to find out what they 

 are. As I wish, when opportunity offers, to resume the in- 

 vestigation of these remarkable rotifers, I shall not now 

 append any drawings, or discuss minute details of their orga- 

 nization. Their name designates an astounding peculiarity — 

 the absence of a bowel or anus, which might have been thought 

 indispensable to a creature so highly organized as the asplanchna 

 undoubtedly is. 



The Asplanchna BrighiwelUi is almost a twenty-fourth of 

 an inch long. The jaws are called " one-toothed," but the 

 appellation is scarcely correct, as these organs consist of two 

 arms, cleft at their extremities, and having a large toothed 

 projection rather less than half-way down. A carefully-made 

 drawing is before mo as I write, and the general impres- 

 sion, when the cuiwed arms (rami and mallei) aro placed 

 upright, is not unlike that of a pair of antlers, and they do 

 not seem much better fitted for anything like chewing the food 

 that passes through them. Whatever is swallowed goes down 

 a conspicuous gullet, and a very extensible crop, often seen in 

 folds, and abounding in delicate muscular bands. My hope was 



to find that Hiis was in some way divided, and that there 

 existed ;i dist inct exit -pipe. In this! was unable to succeed, and 

 I can offer no explanation of the riddle winch the asplanchna 

 presents. The crop terminates in a stomach of rounded, but 

 irregular form, and when the creature is quiet, the long ovary 

 is folded in a horseshoe round the digestive bag. This ovary 



* Since writing the above, Mr. Gosso, lias allowed mo to see his collection of 

 drawings of these creatures, and, as might be expected, they are far superior to 

 any others. The asplanchna requires to bo studied in a series of sketches. 



