CHAPTER X. 
M0LLUSC01DA. 
“ Nature geometrisetb and observetli order in all tilings.” 
Sin Thomas Browne. 
Bryozoaires, or Polyzoa, as British naturalists prefer to call them, 
the boundary-line which divides the humble mollusc from the 
Ambler zooplxytes. In consequence of this intermediate organi- 
^tion, these creatures were long considered as polypes ; but De Blain- 
v 'Ue, Milne Edwards, and Ehrenberg almost simultaneously began to 
s fparate them from the molluscs, and form them into a separate group. 
®lbse<pient naturalists, while considering the Molluscoida as truly and 
wholly molluscous, admit that the distinction proposed by the French 
^Uralists are most important, and should be retained as a primary 
^division, confining it to those molluscs which have the neural 
re 8ion comparatively little developed, and the nervous system reduced 
j' 0 a single or at most a pair of ganglia, and the mouth surrounded 
b y a more 01 . i ess perfect circlet of tentacles : an arrangement which 
' Vo Md include the Brachiopoda, with the Polyzoa. 
Marine plants are sometimes observed to be quite covered with a 
H1 My parasitic matter, which may at a first glance be mistaken for a 
lll0ss - This apparent mo 3 S, however, is simply an aggregation of 
lt,J iiUalcules, each of which has its separate cell, which is placed quite 
C( »uti 
jl guous to its neighbour. 
. IVse little creatures thus form an entire community. — — 
^ formed by the shin which has been encrusted by calcareous salts, or 
?. ‘ ev organic matter, hardened after the manner of a horn. This 
of shell prot e C t 8 the animal from the attacks of its enemies. 
Uiode'of retreat at the bottom of a protecting shelter is very 
■‘Ttently adopted in the whole series of molluscs. The oyster shuts 
Each cell 
