312 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Porifera. 



New Calcareous Sponge.* — F. Urban describes a new member of 

 the heteroccelous calcareous sponges — Hhabdodermella nuttingi g. et sp. n., 

 from Monterey Bay, California. As its elongated flagellate chambers 

 do not open directly into tho oscular tube, but communicate with it by 

 efferent canal, the new sponge belongs to the family Sylleibidee, beside 

 the two genera — Polejna Ldf. and Vosmaeria Ldf., from both of which 

 it differs a little in the nature of its spicules. The skeleton consists 

 of triactine and tetractine megascleres and rhabdon microscleres ; the 

 needles are dermal and gastral, not parenchymal, recalling an Am- 

 phoriscus-likc arrangement. 



Protozoa. 



Significance of Ionisation in Acclimatisation.f — Dr. E. Florentin 

 considers that tho part played by ionisation in the acclimatisation- of 

 fresh-water organisms to a saline medium has not been sufficiently em- 

 phasised. If an Infusorian be placed in a solution of common salt, the 

 regulation of the pressure between the surrounding fluid and that con- 

 tained within tho cell does not take place by simple osmosis. The 

 internal pressure is due to the ions and to the different molecules of the 

 cytoplasmic medium. If a certain number of saline molecules are in- 

 troduced into the cell the osmotic pressure increases, but at the same 

 time the disassociation of the saline molecules of the same kind, which 

 are already present in the Infusorian, diminishes, because it is known 

 that the proportion of ionised molecules in a solution becomes less as 

 the solution becomes more concentrated. In other words, the numerical 

 augmentation of the particles introduced is compensated in whole or in 

 part by a regression of the ionisation, with the final result that the 

 internal osmotic pressure varies very little. In consequence the internal 

 and external pressures are not equal, and in order to produce equili- 

 brium capillary pressure intervenes and, according as it is greater or 

 less than the elasticity of the cell-membrane, we have or have not 

 changes in the form of the cell. The diminution of ionisation within 

 the interior of the cell when placed in a saline medium, explains Bal- 

 biani's experiments with Paramcecium. Balbiani found that specimens, 

 removed from a solution of common salt to an isotonic solution of 

 potassium chloride, survived much longer than those removed from 

 fresh water or placed in the potassium chloride. The explanation is, 

 that in the first case the presence in the interior of the cell of CI ions 

 produced by the disassociation of the NaCl molecules, diminishes the 

 number of CI ions produced by tho disassociation of the KC1 molecules, 

 and therefore diminishes the number of K ions as compared with the 

 number in the second case where CI ions did not previously exist, and 

 it is the K ions which are so harmful. The same fact explains how it 

 is that organisms can be gradually acclimatised to media of progressive 

 salinity. 



Heliozoa around Geneva.} — E. Penard has descriptive notes on a 

 number of forms, including Actinophrys vesiculata sp. n., Actinosphserium 



* Zeitachr. f. wiss. Zool., Ixxi. (1902) pp. 2G8-75 (1 pi. and 1 fig.).] 

 t Ann. Sci. Nat. (Zool.), xiii. (1901) pp. 305-10. 

 J Rev. Suisse Zool., ix. (1901) pp. 279-305 (1 pi.). 



