RECENT ADVANCES IN SCIENCE 641 



A long and important paper by N. L. Bowen on " The 

 Later Stages of the Evolution of the Igneous Rocks " may- 

 receive brief mention here, but is deserving of a much more 

 extended notice (Journ. GeoL 1915, 23, Supplement, p. 91). 

 The chief conclusions are that assimilation is relatively unim- 

 portant as a factor in the production of the diversity of igneous 

 rocks ; and that while differentiation is controlled entirely by 

 crystallisation, the arrangement of the separated units is 

 effected under the influence of gravity. 



C. K. Leith and W. J. Mead, in continuation of their 

 " Metamorphic Studies " {Journ. GeoL 191 5, 23, 600), develop 

 the view that the formation of slates, schists, and some gneisses 

 by rock flowage, requires a convergence, both chemical and 

 mineralogical, towards a few columnar or platy minerals, which 

 give these rocks their characteristic lamellar structure. 



J. Johnston discusses the available experimental evidence 

 as to the function of pressure in the formation of rocks and 

 minerals (Journ. GeoL 191 5, 23, 730), and comes to the con- 

 clusion that its effect on the equilibrium of a polycomponent 

 chemical system is not especially marked unless one or more 

 of the components is volatile. 



ZOOLOGY. By C. H. O'Donoghue, D.Sc, F.Z.S., University College, 

 London. 



Protozoa. — Bentham has examined " Some Protozoa from 

 Fishes occurring in the Vicinity of Cullercoats, Northumber- 

 land " (Ann. and Mag. Nat. Hist. November 191 5). He finds 

 Hsemosporidia parasitic in Coitus scorpius, Scomber scomber, and 

 Rata baits, and also a species of Trichodina on the gill-rakers 

 of the first named . 



Invertebrata. — Three new species of Alcyonaria and a 

 Stylaster from the west coast of North America are described 

 by Hickson (Proc. Zool. Soc. 1 October 1915). A collection 

 of Land Planarians was made by members of the British 

 Association in Australia and has been described by Dendy 

 (ibid. November 191 5). Three species all new were obtained 

 from West Australia, and of the six species from Tasmania 

 two are new. The first Land Nemertean, a new species, to be 



1 In the case of papers in the Proceedings of the Zoological Society the date 

 given is that on which the paper was read and not the date of publication. 



