236 Messrs. Alder and Hancock on a new British species 



stem, lias been observed also by us in Eolis, with this difference, 

 that while in Calliopaa there are two longitudinal vessels running 

 the whole length of the body, in Eolis there is only one of these 

 vessels, sending off branches to the papillae. The passage of 

 particles of matter from these vessels into the papillse and back 

 again in an irregular manner may occasionally be observed. 

 These particles are of various sizes and forms, and have a 

 crude undigested appearance. They are occasionally mingled 

 with regular blood-like globules. Their motion is produced by 

 the contraction of the walls of the vessel and of the stomach, 

 which is every now and then perfectly collapsed. There is no 

 decided onward current produced by this action, which takes 

 place quite irregularly in different parts of the gastro-vascular 

 system, but a mere oscillatory motion in the immediate vicinity 

 of the action. We have observed another curious circumstance 

 apparently connected with this system, which appears to have 

 escaped the observation of M. Milne Edwards, and for which we 

 can in no wise account. The end of each of the papillae has in- 

 ternally a small ovate vesicle, which is connected by a transpa- 

 rent vessel with its central tube. By the contraction of this ve- 

 sicle very minute bodies are occasionally sent out by a small aper- 

 ture terminating the papilla. These bodies are of an elliptical 

 form, with a long hair-like tail, and bear considerable resem- 

 blance to the Spermatozoa, but have no motion, nor is the organ 

 from which they issue at all connected with the generative func- 

 tions. We would therefore call the attention of comparative ana- 

 tomists to this fact. 



The functions of the gastro-vascular system as well as of the 

 papillse, which have generally been considered to perform the 

 office of branchiae, require further investigation. M. Quatrefages 

 appears to think that the central coloured portion of the papillae 

 performs the functions of the liver ; an opinion which is perhaps 

 correct, but requires further investigation. 



The fact, which we do not recollect to have seen stated, that 

 the whole surface of the body in Eolis, as well as the papillae, is 

 covered with vibratory cilia, might lead us to infer that the or- 

 gans of respiration are not specialized in this genus, but that the 

 animal breathes over the whole body. The appendages in Eolis as 

 well as in Melibcea are very deciduous, which is not usually the case 

 with an important vital organ, and the animals are known to live 

 for some time when deprived of them. But even though the 

 papillae should be considered the chief seat of the respiratory 

 function, it is evident that they have at least some other office to 

 perform, the nature of which is not well understood. 



Dr. Siebold has announced the discovery of the organs of hear- 

 ing in many of the pulmoniferous Gasteropodes as well as in se- 



