438 J. H. ORTON, 



water. The collected food material is washed towards the mouth in 

 two main batches, according to whether it is coarse or fine. The coarse 

 particles on being drawn in with the water can be seen to be washed 

 forwards along the left side of the animal towards a pouch which hangs 

 down in front of the mouth. (See Figs. 1 and 2 A.) In this pouch 

 the particles collect, and Crepidula can feed when it wants. The 

 greater part of the fine particles, however, are treated differently. 

 These, on being drawn against the gills, are washed towards the tips 

 of the gills, which just roof in a deep groove on the right side of the 

 animal. (See Fig. 1 B and Fig. 2 B.) In this groove the fine particles 

 are collected, and every now and then are shot forward towards the 

 mouth in a cylindrical mass. (See Fig. 1 B.) As the food mass passes 

 forward, the animal seizes it in its mouth and eats it. I have fed 

 Crepidula on diatoms, and watched it feeding in this way, and if very 

 fine coloured particles be added to the water, a coloured cylindrical 

 mass may be seen collecting on the right side of the animal just behind 

 the " head," and the action of swallowing easily observed. Examination 

 of the gut contents of Crepidula and the oyster shows that the same 

 kinds of diatom are found in both animals, and moreover, that the 

 commonest diatoms are the same in both animals. The fasces of slipper- 

 limpets fed on a culture of diatoms consist wholly of diatom shells 

 embedded in mucus. Thus it will be seen that Crepidula can be fed 

 on diatoms. A chain of six individuals lived for nine months in a 

 large-sized jam jar which contained sterilised water, to which supplies 

 of diatoms and other small organisms were added at intervals. At 

 present there are in our tanks a large number of living chains which 

 have already been there nearly a year, and several other chains which 

 I have had about seventeen months. These are all undoubtedly feed- 

 ing on the floating substances in the tanks. A more detailed account 

 of Crepidula's mode of feeding and of the gut contents of Crepidulae 

 and oysters will be published shortly in the Journal of the Marine 

 Biological Association. 



In accounting for the spread of Crepidula in its new environment, 

 some allowance must also be made for the probable absence of some 

 of the enemies which it had in its original home, and also for the 

 probability of an invigorating effect of the new environment. With 

 regard to this latter suggestion may be noted the apparently early 

 spawning of English Crepidulae. I am informed by Prof. Conklin 

 that American Crepidulae begin to spawn in May and possibly in 

 April, while English Crepidulae begin to spawn in early March.* 



* Since this Report was written, Crepidula spawned in the tanks at Plymouth in early- 

 February. 



