170 Bihliographical Notices. 



provisional and untenable subkingdom with groups of animals with 

 which they appear to have nothing to do. It seems to the present 

 writer that the Echinodermata may fairly stand as forming one of 

 the primary types of animals — that the Turbellaria and Rotifera 

 may be placed without violence in the neighbourhood of the Anne- 

 lida — and that the most natural direction in which to look for the 

 real affinities of the parasitic groups is also among the Annulosa, in 

 which the phenomenon of parasitism, with all its phases of structural 

 degradation, is so familiar to us. We may remark, in connexion 

 with this part of the subject, that Dr. Xicholson quotes, as Prof. 

 Allman's character of the Annuloida, a diagnosis which can apply 

 only to the Echinodermata (p. 135). 



In other respects, it seems to us, Dr. Nicholson has succeeded well 

 in his object of producing a useful handbook for students of zoo- 

 logy. His introductory essay on the principles of zoology contains 

 good and useful ideas, clearly and intelligibly put before the reader, 

 except that here, as indeed throughout the book, the author has 

 indulged rather more freely than is desirable in the direct use of 

 technical terms. Upon the vexed question of the origin of species 

 our author leaves his readers to form their own opinions. 



In classification, as we have already stated, Dr. Nicholson foUows 

 Professor Huxley in his broad outlines, filling up the details from 

 the works of other authors. The classification is in all cases carried 

 as far as the orders ; and under most of these, synopses of the families 

 are given. The illustrations, although by no means admirable as 

 works of art, are generally distinct and intelligible, and quite suffi- 

 cient to give the student a clear idea of the objects described in the 

 text. 



We have noticed a few minor points in which, it seems to us, 

 Dr. iSTicholson's manual is susceptible of improvement. The author 

 frequently uses the term " mimetic " to express a general resemblance 

 or " homomorphism " of different organisms when no " mimicry " is 

 in question; and this will be Hable to mislead his readers. At p. 95 

 he uses the term Discophora for a subclass of Hydrozoa, quite dif- 

 ferent in its limitations, so far as we are aware, from any group to 

 which that term has been applied — including, namely, those naked- 

 eyed Medusae whose origin by gemmatiou from a polype-like foi'm 

 has not yet been demonstrated. We do not think that the group 

 should be maintained ; but at any rate some other name should be 

 given to it. There is some confusion as to the true position of Hya- 

 lonema: first (p. 116) it forms a family of Sclerobasic Zoantharia ; 

 then (p. 117) the opinion that Ni/alonema should be placed among 

 the siliceous sponges is said to be probably the true one ; but again 

 (p. 123) the Hyalonemadae appear as a family, and the characters 

 of their coraUum are indicated. To a student this wiU prove rather 

 puzzling. Among the Crustacea no notice is taken of those remark- 

 able parasitic allies of the Cirripedes, Feltogaster &c., of which Fritz 

 Miiller has formed the subclass Rhizocei)hala ; the order Lsemo- 

 dipoda is retained, although it is now generally admitted to have 

 been founded merely upon abnormal forms of Amphipoda ; and the 



