466 Miss M. Greenwood. On the Constitution and [Dec. 14, 



December 14, 1893. 



Sir JOHN EVANS, D.C.L., LL.D., Treasurer and Vice-President, 

 followed by Professor J. S. BUKDON SANDERSON and Sir 

 G. M. HUMPHRY, in the Chair. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The Right Hon. James Bryce, a Member of Her Majesty's Most 

 Honourable Privy Council, whose certificate had been suspended, as 

 required by the Statutes, was balloted for and elected a Fellow of the 

 Society. 



The following Papers were read : 



I. "On the Constitution and Mode of Formation of Food 

 Vacuoles in Infusoria, as illustrated by the History of tbe 

 Processes of Digestion in Carchesium polypinum" By MARION 

 GREENWOOD, Girton College, Cambridge. Communicated 

 by J. N. LANGLEY, F.R.S. Received October 28, 1893. 



(Abstract.) 



Since the time that Ehrenberg first formulated his celebrated 

 " polygastric " theory, there have been few writers on the Infusoria 

 who have not confirmed his observations while combating the inter- 

 pretation of them given by him. For it was shown long ago that the 

 " Magenzellen " of Ehrenberg are spherical food masses, and these, 

 circulating with varying rapidity in the " endoplasm," are so striking 

 optically in most Infusoria that the literature of this group abounds 

 in descriptions of or references to them. There is, however, a lack of 

 any details which would throw light on the precise mode of origin of 

 these ingesta, and yet this point has interest, for, while relatively 

 large food masses are swallowed by certain of the ciliate Infusoria, 

 very many forms are adapted only for the inception of minute solid 

 particles, which seem far removed from the relatively large masses 

 so noticeable within the animals. 



An extreme case of this disparity between the size of ingested 

 particles and the size of food masses circulating within the body is 

 found in almost any member of the VorticellideB ; the form I have 

 chosen for examination is Carchesium polypinum, which grows in 

 pedicellate clusters, each polype being mounted on a highly retractile 



