134 The Irish Naiuralisi. June, 



As a rule, when a parasite retains to some extent the power of loco- 

 motion, the general structure of the adult does not differ greatly from 

 that of the free-living t^-pes. But parasitism and its general effects in 

 producing structural changes can be studied, to great advantage, among 

 the Crustacea. In some Copepod crustaceans the female only is para- 

 sitic and becomes modified, the male remains free-swimming. Occasion- 

 ally, as in the Monstrillidse, which are endo-parasitic within polych^et 

 annelids, the adults of both sexes are free-swimming, but are without 

 mouth-parts or alimentary canal. All intermediate conditions of para- 

 sitism between the extreme cases of Sacculina and Peltogaster, which 

 are modified almost beyond recognition, and the simple Copepods, living 

 on the excretions of the skins of fishes, occur. 



Dr. Caiman's account of these is fascinating. And yet, even in read- 

 ing his description of the interesting Anaspides, which we are so familiar 

 with from his own researches as one of the few forms preserved to us 

 with little change from Carboniferous and Permian times, we feel a 

 certain disappointment at the comparative neglect of two great branches 

 of the subject which the modern naturalist would expect to find in a 

 great work of this kind. Of the geographical distribution of the 

 Crustacea there is little, while the remarks on their habits and the 

 manifold waj's in which their modes of life affect our industries, are 

 often too cursory. This is the only serious fault in a work which is well 

 illustrated, excellentl}' written, and carefully brought up to date. 



R. F. S. 



BRITISH AND IRISH DESMIDS. 



A Monograph of the British Desmldlaceae, By W. West, 

 F.L.S., and G. S. West, M.A., D.Sc. Vol. i., pp. xxxvi. -j- 224, 

 Plates i.— xxxii., 1904 ; vol. ii.. pp. x. + 204, Plates xxxiii.— Ixiv., 

 1905 ; vol. iii., pp. xv. + 274, Plates Ixv.— xcv., 1908. London (Ray 

 Society). Price 255. net per vol. 



There is no one better qualified to write a work on such a subject than 

 the two authors who have undertaken this Monograph. Certain it is 

 that as regards Ireland most of our knowledge of the distribution of 

 Desmids and of Freshwater Algae generally in the northern and western 

 parts of the country is due to their investigations. 



The work begins with a short historical account of previous studies on 

 the group. Ralfs' "British Desmidiese," published in 1848, enumerated 

 162 species and 32 varieties as occurring in the British Isles. The 

 account of Desmidiese in Pritchard's " Infusoria," 4th ed., t86i, was 

 written by William Archer, who was for many years one of the leading 

 members of the Dublin INIicroscopical Club, and to whose work a just 

 tribute is paid by the authors of these volumes. Cooke's "British 

 Desmids," published in 1887, contained descriptions of 290 species and 48 

 varieties. In the present work about 750 species and 450 varieties will 

 be described. Apparently two more volumes will complete the work. 



