176 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the hydrogen ion by the cell follows the laws of adsorption. The 

 equilibrium between the external solution and the cell is apparently 

 established by means of the outer membrane of the cell. This process 

 constitutes lioeb's " membrane effect." J. A. T. 



INVERTEBRATA. 



Mollusca. 

 y. Gastropoda. 



Pulsating- Organ in Hyalin lucida. — G. Meraiod {Revue Suisse 

 Zool., 1920, 28, 119-24, 1 fig.). In this carnivorous snail there is a 

 small pulsating organ, visible with the naked eye, situated in the sub- 

 terminal region of the ureter, close to the opening of the shell. In a 

 snail with a shell a centimetre in diameter the pulsating organ is about 

 a millimetre in length by half a millimetre in height. There is no 

 regularity in the pulsations ; while the heart had .50 pulsations in a 

 minute, the organ had 76, 80 or 100. The body of the organ consists of 

 a loose network of connective cells and darkly pigmented cells ; its 

 root is in the circular vein of the pulmonary cavity. It may be a sort 

 of secondary heart, facilitating the return of the blood from the circular 

 vein. Or it may be an organ that drives excreted particles into the ureter. 



J. A. T. 



5. Lataellibranchiata. 



Nutrition in Lamellibranchs. — D. Carazzi {Rassegna Sci. Biol., 

 192u, 33-5(), 2 figs.). A discussion of the mode of nutrition in oysters, 

 with an account of experiments. In 1896 the author came to the con- 

 clusion, afterwards re-affirmed by Piitter (1908), that oysters absorb 

 nutritive material in absorption in the water. To this he firmly adheres. 

 The main mode of nutrition in Lamellibranchs is by absorption of 

 substances in solution in the water. The absorption is by means of 

 the epithelium of the intestinal mucosa, the labial palps, the branchial 

 lamellae, and the edge of the mantle. According to Carazzi, is is only 

 in a secondary way that Lamellibranchs feed on plankton organisms. 



' J. A. T. 



Animals Associated with Spondylus. — Charles Perez {Comptes 

 Rendus Soc. Biol, 1920, 83, 1027-9). On the pearl banks of the 

 Persian Gulf there is a frequent occurrence of Spondyhis gaederopus. 

 This bivalve always contains either the Pontomid crustacean Anchistus 

 niiersi (a pair) or the Pinnotherid Ostracotheres spondyli (invari- 

 ably a female). The Pinnotherid harbours two parasitic crusta- 

 ceans, usually one or the other — namely, a new Bopyrid, Rhopcdione 

 uromyzon (both sexes), fixed under the abdomen, and SaccuUna ostraco- 

 theris. But the Sacculina harbours a group of Cryptoniscids — several 

 adult females, numerous males, and some transitional forms between 



