ON THE PRINCIPLE OF CEPHALIZATION. 169 



poles of the body, though, even here, according to "Wood- 

 ward's Treatise on Mollusca," page 204, Forskahl an 1 

 Lamarck "compared Hyalea with 'lerebratula ; but they 

 made the ventral plate of one answer to the dorsal valve 

 of the other, and the anterior cephalic orifice of the pter- 

 opodous shell correspond to the posterior, byssal fora- 

 men of the bivalve !" And, if the views I advance prove 

 correct, they were precisely right. In all my previous at- 

 tempts to homologize the different classes, I had always 

 met with an obstacle in the apparently aberrant characters 

 of the Brachiopods : never for a moment doubting the truth 

 of the accepted views, that indicated the regions to be 

 called dorsal and ventral, as such, I labored in vain. 

 When I undertook to interpret the relation of these classes 

 on the principle of cephalization, I found that these ac- 

 cepted views must be doubted, and it was with amaze- 

 ment that I beheld such unlooked for results : that the so- 

 called anterior pole is really the posterior pole, and that the 

 so-called dorsal region is really the ventral region. 



It has not been without patient consideration that I now 

 advance these views, knowing that by many they will be 

 received with oppo©ition ; nevertheless, the more I try to 

 make them comformable with already received relations, 

 the more I am convinced that such relations are wrong; 

 and it is only in believing that continued research will 

 but confirm these propositions, that I now dare to offer 

 them. 



According to the views here advanced, the Brachiopods 

 are attached by a prolongation from the dorsal area, as in 

 the lower Polyzoa, where they lie on the back. That in their 

 natural position in life, this valve is really uppermost. 

 That the process of attachment also proceeds from the an- 

 terior pole of the body, as in all the members of the Branch 

 even to Gasteropods, with the exception of those attached 

 by one valve, (e. g. Ostreans, Clavagella,) whether it be by 

 a byssus, confined in cells of their own making, or buried 

 in the mud, it is the anterior end which is fixed. In sev- 

 eral lower forms, like Tridacna and Anomia, the point of 

 attachment springs from the dorsal area, as in the two low- 

 est classes. In regard to the posterior position of the 

 mouth in Polyzoa and Bracbiopoda, we have similar anal- 



ESSEX INST. PROCEED. VOL. IV. V. 



