ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 565 



not form a natural family, but consist of a heterogeneous assemblage of 

 Stellettids which have independently lost their tria^nes. 



The progressive evolution of the sponges as a whole has been a 

 gradual process of increase in complexity of structure, due to colony 

 formation and integration, in which branching and budding, folding and 

 secondary fusing, have played the chief parts, while the skeleton has 

 constantly become adapted to suit the new mechanical requirements. 

 " Though species seem frequently to have arisen as mutations in trivial 

 and non-adaptive characters, evolution, on the whole, seems to have taken 

 place by a process of progressive evolution, in which mutation has played 

 a comparatively small, though by no means negligible part." 



Notes on Aphrocallistes beatrix.*— Isao Ijima discusses this very 

 variable species of Hexactinellid sponge, widely distributed in the 

 Pacific, Indian, and Atlantic Oceans. Those in Eastern Asiatic seas 

 have certain features in common, and may be designated Aphro- 

 callistes beatrix orientalis. There is a somewhat diminutive development 

 of macroscopic body-parts, and there are several characteristic features 

 in the spiculation. Tlius the dermalia are largely pentactine ; the 

 leptoscopules are always small, bulb-like, and beset with whorls of 

 minute barbs ; and there are elongate forms of hemihexasters not over 

 100 /u, in length. 



Siberian Fresh-water Spongcf — Nelson Annandale describes 

 SponjiiUa {Euspongilla) arctica sp. n., from some arctic lakes in north- 

 western Siberia. The structure of the skeleton is peculiar and cha- 

 racteristic. It consists in the main of slender spicule fibres, each of 

 which is encased in spongin. The fibres arise from the basal mem- 

 brane, with which their investment is in direct continuity, and run 

 upwards, sometimes in a slanting direction ; in their course they branch 

 frequently in a dichotomous manner, and delicate webs of spongin extend 

 across the forks, often containing circular or oval apertures. Single 

 spicules or indefinite transverse fibres run occasionally from one branch 

 to another, carrying with them the investment of spongin. In addition 

 to the organized skeleton, there are numerous loose megascleres lying 

 free in the substance of the sponge and forming an irregular layer 

 at the base. They are particularly numerous in the neighbourhood of 

 gemmules, and sometimes form regular cages either round single 

 gemmules or round groups of gemmules. These cages consist of spicuks 

 lying more or less parallel to one another in a membrane of spongin. 

 In these skeletal features the new species seems to resemble Ephydatia 

 okhonensis, from I^ake Baikal. 



Protozoa. 



Soil Protozoa. I — T. A. Goodey describes a number of Protozoa from 

 agricultural soil. The first is Proivazekia {Bodo) saltans Ehi-bg., a bean- 



* Annot. Zool. Japon, ix. (1916) pp. 173-83. 



t Mem. Acad. Imp. Sci. Petrograd, xxviii. (1915) No. 9, pp. 1-8 (4 figs.). 



+ Proc. Zool. Soc, 1916, pp. 309-32 (4 pis. and 1 fig.). 



