REPORT OX THE PEXNATULIDA. 247 



absent we might find in this the explanation of Virgularia being 

 habitually devoured as food, while Fitniculhui and Pennatula are 

 allowed to go uuharmed. 



This explanation is of course a purely hypothetical one, resting 

 merely ou our inability to find thread-cells in imperfectly preserved 

 specimens. We have thought it worth while to record it, however, as 

 it is one which the Society may have an opportunity at some future 

 time of testing directly, and also because we know of certain other 

 facts which seem to make it uot altogether improbable. Thus we 

 know from the observations of Kolliker, Koren and Danielsseu, and 

 others, that the truncation of the upper end occurs normally in certain 

 species of Virgtilaria, but not in others ; i.e., according to our theory, 

 that certain species of Virfjiilaria are habitually eaten as food by fish or 

 other marine animals, while other species escape. We know also from 

 an observation of Rumph made more than a century ago, that some 

 species of Virgularia possess a very remarkable power of stinging, due 

 evidently to the possession of thread-cells, while in other species this 

 stinging power is not perceptible, at any rate to ourselves. 



Eumph's observations are so important that we shall quote them 

 here. His specimens of Vlrgularia, of a species which has been since 

 named by Kolliker, in honour of its discoverer, Virqularin Ruinphu, 

 were obtained at Amboyna, a sinall island in the Malay Archipelago, 

 east of Celebes. Concerning them, he says :* — " If one handles them 

 incautiously one experiences a burning sensation, and the hand 

 becomes x-ed ; then ensues a violent itchiiig, followed by the appearance 

 of jjustules, as if one had been stung by nettles, lasting for three days." 

 Concerning another species, Viriiuliirinjitucen, Rumph remarks that he 

 has not noticed that it causes any distinct burning or itching in the hand, 

 although he had pulled them up by hundreds. Neither does Darwin, in 

 his account of the South American J'irtiularia, say anything concerning 

 it possessing a power of stinging, which he could hardly have failed to 

 notice had it been actually present. We know also that both of these 

 latter species are habitually truncated, so that there seems sufficient 

 evidence to warrant our making the suggestion that Virgularia mirabUi!^ 

 may be devoured because it possesses no thread-cells, while Fumculina 

 escapes because it is richly armed with these defensive weapons. 



d. The Stomach. — The mouth, as shown in Fig. 5, m, is situated on 

 the apex of a small papilla that rises up in the middle of the circle of 

 tentacles, the outer wall of the papilla being continuous with the bases 

 of the tentacles and the inner with the wall of the stomach. The 

 mouth is a transverse slit (Fig. 7), whose long axis is at right angles 

 to the flat surface of the leaf. The varying position of the mouth in 

 different conditions of protrusion or retraction of the polype is well 

 shown in the several polypes of Fig. 5. When the tentacles are 

 completely retracted, as in the second and seventh polypes, the mouth 



* Rumph : " T' Araboin 'sche Rariteitkamer," p. 43, Amsterdam, 1741. Wo have 

 been uuable to refer directly to this work, and take our account from a quotation 

 iu KolHkor's "Alcyouarion," p. :201. 



