148 



SCIENCE-GOSSIP. 



STRUCTURAL FEATURES IN AMERICAN ROTIFERA. 



By Dr. Alfred C. Stokes. 

 {Continued from page 122.) 



Taphrocampa selexcra, Gosse. 



npHIS interesting larviform creature is not com- 

 men in my vicinit}-, but from a single shallow 

 pool near my home it has been taken sparingly, the 

 locality having, perhaps, supplied me with half-a- 

 dozen specimens, over which I have observed a few 

 structural points which appear not hitherto to ha\-e 

 been noticed. The rotiferon is an untidy animal, 

 its cuticular surface always being more or less 

 defiled by adherent particles of various kinds, while 

 the creature itself has a fondness for rooting 

 among dead matter, and for eating even the 

 excrement of vi^orms and of aquatic snails. 



Gosse says nothing about the antennae ; I assume, 

 therefore, that he failed to see them. Still, in all 

 his descriptions, he almost systematically omits 

 references to these organs, which should have been 

 included in every diagnosis, even at the risk of 

 repetition and of a loss of rhetorical grace. No 

 one would voluntarily go to a technical monograph 

 with the expectation of meeting with the beauties 

 of rhetoric, nor with quotations from Latin poetry, 

 nor with a supply of "elegant extracts." Space 

 occupied by literary graces would better be filled 

 with complete descriptions of the objects treated. 



It may be that the American forms of Taphro- 

 campa are varieties of the European, with the 

 antennse and the frontal cilia v.-ell developed, while 

 in the British specimens these parts are obscure. 

 In my specimens of T. selemira, there are two dorsal 

 antennas at the front, each a setigerous, truncated 

 lobule, while the lateral ones are minute papilla:, 

 elongated and setigerous. The frontal cilia are 

 short and fine, but well developed, filling an 

 entirely prone, obovate field, about one-fifth the 

 length of the body. The}- are visible only in 

 lateral or in ventral view. The brain is not entirely 

 opaque, the opacity being confined to a granular 

 mass in the posterior region, yet there is reason 

 to believe that the opacity increases, or at least 

 changes, with the age of the animal. 



The cesophagus is long and conspicuous, and an 

 ovoid gastric gland is adherent to each frontal 

 shoulder of the stomach. Within the stomach and 

 across the entrance of the oesophagus is again the 

 membraniform but really tubular organ so often 

 referred to in other American rotifera, it being 

 here, as elsewhere, an actual prolongation of the 

 cesophagus. Its undulations are constant, but 

 when food is passing through the cesophagus the 

 movements become bewilderingly rapid, especially 

 so as the observer has to contend with the constant 



writhings of the animal itself, such conditions 

 making it impossible to decide positively that the 

 food particles do pass through this tube, although 

 they may be flowing into the stomach in a steady 

 stream. Does this internal appendage exist with 

 Taphrocampa saudersia, Gosse, and with T. annulosa, 

 Gosse ? These species have been taken in this 

 country only in the State of Michigan, by Mr. H. 

 S. Jennings, who gives no notes of their structure. 

 If it is present in T. clavigera (i) I failed to notice it. 

 Neither were the lateral antennae seen on that 

 species, although they must be present. 



The entire alimentary canal of T. selemira is 

 ciliated. When the posterior region is empty, the 

 organ is a continuous, uninterrupted tube. But 

 when the posterior portion contains excrementitious 

 matters, a constriction occludes the lumen, thus 

 temporarily dividing the tube into two subequal 

 parts functionally distinct. The contractile vesicle 

 is single, comparatively large, and ventrad to the 

 intestine near the posterior extremity. Several 

 flame-cells are visible on each side of the alimentar}" 

 canal. Auricles are present, but seldom protruded. 

 In the few instances in which I have seen them, 

 they appeared to be cup-shaped, the cilia lining the 

 concavity and the margins ; but they may not have 

 been fully expanded, as the animals were not then 

 in a comfortable situation. 



Philodina aculeata, Ehr. 

 The American specimens which I have seen are 

 not nearly so deeply coloured as shown in Gosse's 

 figure, but are, as a rule, onlj^ faintly tinged with 

 brown. The body is densely and finely papillose, 

 a feature not mentioned in the diagnosis of the 

 genus, and therefore presumably not present with 

 European forms. The frontal column is ciliated 

 as described, but it also bears a small cucuUate 

 appendage at the tip, this little hood overhanging 

 and partly surrounding the cilia. The species is 

 not uncommon in this part of New Jersey, where I 

 have captured it during the summer, and taken it 

 from under the ice in February. 



Philodina citrixa, Ehr. 

 The body of the European form is said to be 

 smooth ; the American species are minutely papil- 

 lose, and almost as conspicuously fluted as is 

 Rotifer vulgaris. 



SCARIDIUM LONGICAUDUM, Ehr. 



Gosse's statement that the eyes are permanently 

 (1) Ann. and Mag. Nat. Hist., July, 1S96. 



