644 SCIENCE PROGRESS 



Rhythmic Changes in the Resistance of the dividing Sea- 

 urchin Egg to Hypotonic Sea-water and their Physiological 

 Significance " {Jour. Exper. Zool. Oct. 191 6) puts forward two 

 propositions. " Division results from (1) a definitely localised 

 increase of surface-tension, resulting directly from increased 

 permeability and decreased electrical polarisation of the cell- 

 surface, over two symmetrical areas centring at the poles and 

 extending to near the equator ; and (2) a secondary or adjuvant 

 effect of the same kind due to the diffusion of electrolytes from 

 the astral centres or centrioles which become chemically active 

 at this time." Lastly we have the " Experimental Control 

 and Modification of Larval Development in the Sea-urchin 

 in Relation to the Axial Gradients " dealt with by Child {Jour. 

 Morph. Dec. 1916). Low concentrations of certain substances 

 bring about differential effects along the axes and seem to 

 show that the investigation of the relation between suscepti- 

 bility and metabolic rate affords a method for the investiga- 

 tion of many tenatological forms observed in nature. 



New species of Mollusca form the basis of : " Notes on the 

 Cephalopoda of the Irish Atlantic Slope " by Massey {Ann. 

 and Mag. Nat. Hist. July 1916) ; " Descriptions of Eight New 

 Species of Marine Mollusca from the South Shetland Islands " 

 by Preston {ibid. Sept. 1916) ; " Pisidium supinum A. Schmidt 

 and P. parvulum Classin, fossil in Ireland," by Woodward 

 {ibid. Oct. 1916); and "Descriptions of Two New Mollusca 

 of the Genera Leptothyra and Mitra " by Sowerby. Churchill, 

 who has studied " The Absorption of Nutriment from Solu- 

 tion by Freshwater Mussels " {Jour. Exper. Zool. Oct. 1916), has 

 no doubt that the mussels may make use of some kinds of food 

 which are in solution in the water. A discussion of " Shell- 

 banding as a Means of Protection " is put forward by True- 

 man {Ann. and Mag. Nat. Hist. Oct. 191 6). 



Crustacean forms are recorded in : " On Paragnathia, a 

 Genus of the Crustacean Family Gnathidse," by Cooper {Ann. 

 and Mag. Nat. Hist. July 191 6) ; " Parapherusa crassipes 

 (Haswell), an Amphipod of Australian Seas " by Chilton {ibid. 

 Aug. 1 91 6); and "A New Species of the Crustacean Genus 

 Squilla from West Africa " by Caiman {ibid. Oct. 1916). Chil- 

 ton also gives an account of " The Gribble {Limnoria lignorum 

 Rathke) attacking a Submarine Cable in New Zealand " {ibid. 

 Aug. 1916). The " Chemical Control of Rhetaxis in Asellus " 



