312 SUMMARY OF CURRENT RESEARCHES RELATING TO 



circumscribed and slow. There is a neuromuscular negatively geotropic 

 response. In quiet water the mouth and distal tentacles are pressed on 

 the mud. lu running water the proximal tentacles entangle food and 

 transfer it to the distal tentacles and mouth. The neuromuscular 

 mechanism of Gorymorflm is not intermediate between that of the 

 receptor-effector system of Actinians and the independent effectors of 

 sponges. It resembles a reduced Actinian system rather than a primitive 

 state from which such a system could be derived. J. A. T. 



Suction in Sea-anemone. — G. H. Parker {Journ. Exper. Zool, 

 1917, 24, 219-22, 1 fig.) has experimented with Crihrina xanthogram- 

 mica, which has great power of suction in its tentacles, and in tubercles 

 which extend in rows from the oral to the pedal disc. The tentacles 

 grip food ; the tubercles grip pieces of shell. The breaking force 

 required to separate fragments of shell from the tubercles was measured. 

 The average for ten trials was 47 "2 grm., and the average suction- 

 pressure was 11 grm. per square millimetre. This amounts approxi- 

 mately to 15 "6 pounds per square inch. As the limit of suction under 

 ■ordinary circumstances is one atmosphere, or 14 "7 pounds per square 

 inch, it appears that .at the moment of breaking the sea-anemone was 

 ■exerting as much suction as, under the circumstances, was physically 

 possible. J. A. T. 



Antarctic Actiniaria. — T. A. Stephenson {British Antarctic 

 <" Terra Nova ") Expedition, 1910. Zoologij, 5, No. 1, 1-68, 6 pis. 

 Printed by order of Trustees of the British Museum, 1918) establishes 

 five new genera — Hormosoma, Lilliella, Artemidactis, Aiptasioides, and 

 L&ptoteichus — and gives careful descriptions of fifteen species, of which 

 •eleven are new. All were collected by the " Terra Nova " Expedition, 

 and seven were obtained in deep water in the Antarctic area. Among 

 the general notes reference is made to nutritive amoeboid cells in the 

 mesogloea, to the presence of zooxanthellse in the male gonads, and to the 

 relative value of diverse structural features. It would seem that the 

 most generally reliable generic characters are to be found in the external 

 features of the body other than its length, in the number of perfect 

 mesenteries, and in the musculature. J. A. T. 



Protozoa. 



Metabolic G-radients in Amoeba and their Relation to Amoeboid 

 Movement. — Libbie H. Hyman {Journ. Exper. Zool., 1917, 24, 55-99, 

 14 figs.) finds in each pseudopodium a gradient in susceptibility to 

 potassium cyanide. It is greatest distally and in the most recent 

 vigorous pseudopodia. The regions of highest susceptibility are thus 

 ■anterior, as in other organisms. The gradient arises before the pseudo- 

 podium appears, and hence the metabolic change which produces 

 increased susceptibility is the primary cause of pseudopodium forma- 

 tion. Evidence is adduced to show that the surface of most amoeboid 

 •organisms is in a state of gelation, and it is argued that amoeboid move- 

 ment must be due to alterations of the colloidal state. Liquefaction or 



