112 Moll, 
MOLLUSCOIDEA. 
a very valuable text-book for the student of this class of animals. The 
introduction, 141 pp., gives a condensed but full account of the present 
state of knowledge as to the organization, development, geographical dis- 
tribution, and classification of the subject, preceded by clear definitions of 
the principal descriptive terms. With regard to some controversial ques- 
tions, he impartially relates the reasons brought forward by the principal 
authors, and advocates the necessity of further research before definitively 
settling some of them, but he decidedly rejects F. Muller’s theory of 
the “colonial nervous system,” and accepts instead of it Joliet’s “ endo- 
sarc,” urging its importance in the economy and propagation of the 
animal in rather general terms. As to the “ brown bodies,” he remains 
still somewhat in doubt, ; acknowledging them to be the residua of the 
decaying polypids, he thinks they may possibly be utilized in some cases 
as nourishment for the new bud. He agrees with E. Ray Lankester in 
urging the Molluscan affinities of the Polyzoa^ comparing their epistome 
with the foot and their crown of tentacles with the gills of the Molluaca^ 
especially the Bivalves, and also of the Brachiopods. Busk’s classifica- 
tion is regarded as artificial, very good for the identification of species, 
but giving no clue to their natural relations ; Smitt’s, as the first serious 
attempt towards a natural system, but rather premature and still uncer- 
tain in many details ; and Barrois’s sketch quite hypothetical. Hincks 
prefers at the present stage to keep separate and clearly discriminate the 
more constant and permanent forms, with due attention to their evolu- 
tionary history and varietal tendencies ; but he acknowledges theoreti- 
cally the higher systematical value of the structure of the single cell 
(zooecium), chiefly of its aperture, compared with the general form and 
growth of the colonies. The first part of his scheme of classification is 
'already given in Zool. Rec. xvi. Moll. p. 107 ; the continuation is as 
follows : — 
Suborder 2— Cyclostomata, Busk. 
(1) JRadicdlata, Orb. Fam. Crisiida’.. 
(2) Incrustata, Orb. Fam. Tuhuliporidce, Horncr- 
idcc, and Lichenoporidcc, 
Suborder 3 — Ctenostomata, Busk. 
(1) Haley onella, Ehrenb. Fam. Alcyonidiidee, 
Arachnidiidee, and FlustrelUdce. 
(2) Stolonifera, Ehlers. 
(a) Orthonemidoi, Hincks. Fam. Vesiculariidcc, 
Bushiidcc, Cylindrceciidce, and Triti" 
cellidce. 
(b) Campylonemidee, Hincks. Fam. Valheri- 
idee, Mimosellidce, and Victorellidce. 
Order PuYLACTOLiEMATA, Allman. No marine species. 
Group Nitsche. 
Order Pedicellinea. Fam. Pedicellinidw and Loxosomidee. 
Sub-class PTEROBRANCHIA, Ray Lankester. Fam. Rhahdo- 
pleuridce. 
In the special part, the author endeavours to give detailed and minute 
