294 Mr. W. Clark on the Animal of Kellia rubra. 



pygmmis, and send it to Bath in a moist state with a small phial 

 of sea- water. It arrived yesterday by the post, and I found therein 

 twelve specimens of Kellia rubra, which being placed in a watch- 

 glass in sea-water showed themselves as lively as if examined at 

 Exmouth. By the superior appliances used I at once saw what 

 I had overlooked at Exmouth, and that Mr. Alder is perfectly right 

 in stating the tube to be open below; all the animals repeatedly 

 inserted the foot into the canal, and by thus displacing its sides, 

 showed distinctly it was an open fold of the membrane ; but the 

 moment the foot was withdrawn, it reverted to its usual perfect 

 tube-like aspect ; indeed the most accomplished observer might 

 be deceived, as it appears ]\I. Philippi was. In fact this canal is 

 a mere prolongation of the mantle, which is entirely open for 

 more than half the ventral range, for the working of the foot 

 and byssal apparatus. 



But Mr. Alder is mistaken in supposing the tube-like fold to 

 be for branchial purposes ; no currents, at least branchial ones, 

 enter therein or issue therefrom ; it is a fold merely subservient 

 to locomotion ; this I perceived to be the case in a very short 

 time, as I found the movements of the foot and tube-like canal 

 to be nearly isochronal and dependent on each other, as when 

 the foot was extended and fixed for a forward movement, the 

 tube was also exserted, and by its muscular retractive power, in 

 contemporaneous action with the foot, the shell was advanced in 

 progression. It will now be asked, where then is the branchial 

 aperture ? This I have also satisfactorily discovered ; it is the 

 posterior opening which has passed for the anus, and is in reality 

 a considerable elongated oval fissure, having its periphery slightly 

 thickened or margined, and divided from the rima magna of the 

 byssus and foot by a strong, narrow, transverse septum ; from 

 the termination of this opening the mantle is closed to the um- 



• bones ; within this fissiu"e I distinctly saw a part of the points of 

 the branchiae, and it was regularly dilated and contracted as the 

 currents of sea-water were received, and after aeration of the cir- 

 culating fluid expelled, in a similar manner to the action of systole 

 and diastole. I must now speak of the anus, which I had also 

 the good fortune to discover ; it is placed at the postei'ior end of, 

 and under the branchial aperture, and is a very minute, and for 

 a part of its length, a disunited pendulous tube ; its orifice is not 

 one-tenth part of the size of the branchial opening; from this 

 internal tube I repeatedly saw the rejectamenta expelled in small 

 cylindrical light yellow or grayish pellets, which, falling within 

 the cavity of the fissure, were instantly ejected; this oval aper- 

 ture cannot even be called sessile, it is only a slit, serving as a 

 common canal, for supplying the branchife with water and for the 

 passage of the faeces ; these are the only tn-o openings in the 



