us 



OONCHinOUL 



COXCHIHKRA. 



the foot, for the extrusion of 

 Ait* This is the pallial sac, 

 _ tar respiration and nutrition are 

 where their xist. project from the mantle, 

 tattoo*. Thar are sometimes very long, and 

 Mrs perforations; sometimes separate, and 

 but in any caw the superior siphon is that 

 , and U called th* anal aiphon, white the office 

 r on* is to conduct the water to the branchiss, whenoe it 

 th* branchial or oral siphon. The structure of these 

 phoa* or tubes i* eminently contractile, and their a|rtures 

 ar. fringed with a number of papilla of great sensibility, capable of 

 grrms; otto* of th* contact of any prejudicial foreign body. The 

 lesiaUur museb is Hilly man or Ms* developed according to the 

 ysslst or Vise eatrJnpment of the*s pert*. 



T1w MTTOOS system is very simple. Symmetrical in the Dimyaria, 

 -si .11 1 sjiMeliinsllilhs If iniis.i Vs They have no true brain. In 

 the l*myun then is a ganglion above the OMophagus on each side of the 

 mouth toward* th* labial palps, connected by a transverse filament, 

 erasing th* oasophsgua. From these ganglions filaments are given 

 off to th* month, anterior adductor, *c. ; and from their posterior 

 edges two Mrvooa branch** go to the stomach, liver, and heart, ovary, 

 and hraachisL A branch of some volume goes down to the foot 

 Th* latoal filament*, after advancing along the internal surface of the 

 posterior adductor, are conjoined into one or two ganglions larger than 

 the anterior one*. These posterior ganglion* give off the nerves to 

 all th* posterior put* ; if the ganglions are much separated u nervous 

 In the JsfmomjKina the system is less 



The senses of these animals are very limited ; and indeed there is 

 no good ground for attributing to the generality of than an;. 

 beyond a sense of touch and taste. That most of tlu-m i . 

 conscious of the presence or abiwnce of light is possible. " Nt 

 having any especial organs for iieeiug, hearing, or smelling," fu> 

 Anthony Carlise, speaking of the common oyster, in hi* ' llui 

 (ration 1 (Ib24), "the creature ia limited to perceive no nil.-. 

 impressions but those of immediate contact; mul \<t , .rv part uf 

 its exterior seems to be sensible to light, sounds, odours, and liquid 

 stimulanta. It is asserted by fishermen that oysters, in . utm. -I 

 beds, may be seen, if the water is clear, to close their shells whenever 

 the shadow of a boat passes over them." 



M. Deshayes goes so far as to say that no especial organ of sense 

 can be detected among them, unless perhaps those of t.uu-li ami 

 taste ; but we must not forget what have been called the eye-specks in 

 Pert**, to the animal uf which Poli gave the name of Anjia, frum !!,, 

 supposed number of its visual organs. The pectens are free swimmers, 

 and, from their rapid and desultory motions, we have hear<l 

 termed the butterflies of the ocean. The manner in whir! 

 motions are executed, especially on the approach of danger, in 

 the possession of a sense analogous at least to that of ordinary 

 vision. These eye-specks may be soen in the pecteu placed nt 

 intervals round tlie thickened edge of the mantle, on the outworks, 

 aa it were, of the internal part of the animal fabric. "As ! 

 tion so vUion" i* a general aphorism, not without it* |..<rti. nlai- 

 exception ; for there is good reason for believing that 

 which in a fixture in it adult state, is furnished with these visual 

 specks. 



Th* following arrangement of the Outduftm proposed by H. Deshayes, is published in the ' Cycloptcdia of Anatomy and Phv.-ii.li.gy ' : 



CLASSIFICATION OF THE CONCHIFERA. 



Families. 



i i ll v: > 

 BIVAI.VIA 



DIMTARIA 



MOXOMTAKIA 



I'KTKIi 



I I < IKWX 



\M M i:\ 



llt'DI 



