582 REPORT OF THE COUNCIL, 



examination of the ingested food of the slipper-limpet was therefore 

 undertaken, and a comparison made with the ingested food of 

 oysters taken from the same grounds. This comparison established 

 the curious fact that both kinds of animals were feeding on almost 

 exactly the same food, that is, the various kinds of organisms found 

 floating in the sea. After this conclusion had been arrived at, the way 

 in which the slipper-limpet obtains its food was discovered. This 

 observation confirmed the conclusion tliat the slipper-limpet feeds on 

 the same food as the oyster, for it was found that it feeds in essentially 

 the same way as the oyster, namely, by using its gill as a water-pump, 

 and at the same time as a sieve for filtering the organisms from the 

 water-current it produces. It was therefore made clear that the 

 slipper-limpet is a keen competitor with the oyster for food and space. 



This report was followed up by investigations leading to an explana- 

 tion of the mechanism of the food-current in the slipper-limpet, the 

 oyster, and other Gastropods and Lamellibranchs, and to slight addi- 

 tions to our knowledge of the mode of feeding in the Oyster, the Scallop, 

 the Cockle, the Mussel, and some other bivalves. 



Mr. Orton has also been occupied with general studies on the 

 invertebrate fauna of the neighbourhood. A special feature of the 

 collecting during the year has been the working of a fresh piece of rich 

 shore collecting-ground immediately north of the Mewstone, where 

 large gatherings of Bchinus miliaris, Cucumaria scmicola, Cucumaria 

 normani, and many other invertebrates have been made. Investigations 

 are being made on the apparent pairing habits of Echinus miliaris and 

 on the question of specific difference in the two species of Cucumaria 

 mentioned above. A research on rate of growth in invertebrates has 

 been begun by laying down marked bottles on the various grounds in 

 Plymouth Sound. Useful material for this research was obtained last 

 September from the floating raft moored in Cawsand Bay. 



Mr. L. E. Crawshay has completed his report on the fauna of the 

 deeper portion of the English Channel to the south-west of the Eddy- 

 stone, a region which was practically unexplored previous to his 

 investigations. This report is published in the Journal of tlie 

 Association. In connection with the work. Dr. 11. Hartmeyer, of 

 Berlin, has described the ascidian fauna. 



Messrs. Shearer, De Morgan, and Fuchs published a valuable paper 

 on the hybridization of Echinoids in the Journal in October last, and 

 they have since that time been continuing experimental work on the 

 same subject. 



Mr. G. H. Drew, who holds a Beit Memorial Fellowship for Medical 

 liesearch, has worked at the Laboratory for the greater part of the 



