1906. 
Reviews* 
123 
idealist position, he declares that the idea of duty is the begiuniiig of all 
knowledge. Thus the impression left on the reader's mind as he closes 
the book is one of sharp antithesis— two apparently irreconcilable 
conceptions of his own being both claiming his allegiance. For the recon- 
ciliation and harmonizing of the material and the spiritual outlooks we 
need what underlies even the idea of duty— the faith that behind and 
working through that material universe which is possibly, though not 
certainly, explicable on the mechanical principles for which our author 
pleads, is the Divine Spirit to whom the spirit of man is akin. 
G. H. C. 
THE MOLLUSCA. 
A Treatise on Zoolog^y. Edited by E. Ray Lankaster, LL.D.. 
F.R.S. PartV. IVIollusca. By Paui. PeIvSENEecr, D.Sc. London: 
A. and C. Black. 1906. Pp. 355. Price 15^. net. 
Prof. Pelseneer is best known among malacologists as the originator 
of the most recent and most reliable classification of the Lamelli- 
branchia. At the suggestion of his former teacher, Prof. Ray Lankaster, 
that the gills might furnish characters of classificatory value, he worked 
out the anatomy of the group with considerable skill and patience. He 
constructed on this basis a new classification dividing the L/amelli- 
branchia into five orders. Further researches convinced him that one 
of these, the " Pseudolamellibranchia," should be suppressed, and the 
suborders it contained be merged with the Filibranchia and Eulamelli- 
branchia. This he has carried out in the present work. While these 
anatomical researches are of the greatest value to the systematist, it 
must not be forgotten that the shell of most Mollusca, with its infinite 
variety of valuable characters, will probably always remain as a basis for 
specific determination for palaeontological purposes and for the general 
conchologist. It may be worthy of note that Prof. Pelseneer revived 
Goldfuss' old name of " Pelecypoda " for this class, which designation 
has since been largely adopted in text-books, though he himself now 
reverts again to De Blainville's name of Ivamellibranchia." 
The system of the gill structure and the fundamental character upon 
which the classification is based are somewhat difficult to understand, 
and it would have been well if the author had given us a series of good 
diagrams representing the main features of the system. 
Many excellent new figures have been in troduced, and some attention at 
least has been paid to the life led by the living animal in the chapters on 
bionomics. This is a distinct improvement on some of the previous works 
of the series. Some of the illustrations, however, might with advantage 
have been left out. It is difficult to understand why the old and badl}- 
drawn figures of Ferussac, PfeifFer, and Reeve on page 183, which we 
have seen before in so many text-books, should have again been re- 
produced, when better ones might so easily have been obtained. The 
