SECTIONAL- TRANSACTIONS.— D. 367 



2. ^Ir. J. Gray. — Tlic Mechanism of Cilianj Movement. 



The cilia and the gills of Mj/ti/itx are independent of any nervous control. 

 Their rate of beat depends upon the following factors : (i) Temperature; (ii) de- 

 gree of alkalinity of the cell interior; (iii) presence of o.xygen ; (iv) concentration 

 of potassium ions ; (v) presence of calcium. The amplitude of the beat depends 

 upon the amount of water in the cell. These and other fact.s indicate that 

 the actual contraction is due to the uptake of water by the fibrils when an acid 

 IS liberated at their surface. Since the amount of o.xygen consumed by the 

 cells is controlled by the same factors as those which control the rate of beat, 

 and since the cells are impermeable to anions, it seems likely that the oxygen 

 is used to remove the products formed by the acid when it diffuses away from 

 the fibrils during the period of relaxation. 



3. Di". G. P. Bidder. — The Relation of the Form of a Sponge to 



its Currents. 



Fixed organisms, of animal physiology, depend for nutrition and respiration 

 on the efficiency of the currents which bring them food and oxygen. The 

 outgoing current forms an angle with the incoming streams, which may be 

 called the angle of supply ; between them, unless this be 180 degrees, is a 

 revolving eddy whose diameter may be called the diameter of supply. Through 

 this eddy, in still water, the incoming streams arc polluted from the outgoing 

 stream : the proportion of food-bearing and unpolluted water which reaches 

 the organism increases when either the angle or diameter of supply increases. 

 In sponges (excepting Hexactinellida, which live in immutable bottom-currents) 

 all progressive modification of internal canal-system, or external form, demon- 

 strably increases diameter of supply or angle of supply. Determination of 

 velocity in different regions of a canal system shows them proportional to 

 the needs of a perfect hydraulic engine. 



4. Dr. -\lex.'\nder Bowman. — The Biological Interchange between 



the Atlantic and the North Sea. 



During the course of the investigations being carried out by the Fishery 

 Hoard for Scotland in their Research vessel in the autumn of 1921, special 

 attention was directed to the abnormal hydrographic conditions prevailing in 

 tlie northern part of the North Sea adjacent to the coasts of Scotland. As 

 also in 1920, an unusual incursion of Atlantic water into the North Sea had 

 occurred.' That such occurrences should haA-e profound biological significance 

 will be evident. Apart from the changed physical conditions, such as an 

 increased temperature and higher salinity, the invading water masses bring 

 with them a whole series of organisms not usually found in the North Sea. 

 of which the most striking are perhaps the Saljirr (and more particularh 

 S(d pa fuitiformia). Unusual conditions such as these offer a fruitful ground 

 for research into the probable causation of the distribution of various pelagic 

 organisms, more particularly those belonging to the passively carried plankton. 

 It would also appear that there is some evidence in support of the view that the 

 faiiuro of the great herring-fishery in these two years is not unconnected with 

 these phenomena. 



5. Reports of Committees. 



(a) Zoological Station at Naples. (See p. .315.) 

 {b) Marine Laboratory, Plymouth, 

 (c) Zoology Organisation. 



('(/) Zoological Bibliogrtipliy and Publication. (See p. 316.) 

 (e) Inheritance of Colour in Lejjidcptera. (See p. 318.) 

 (/) Inheritance in Silkworms, 

 (f/) Parthenogenesis. (See p. 317.) 

 (h) Gilbert White Memorial. 

 1922 c c 



