CXll INTRODrCTION. 



they exhibit a close parallelism to the branchial organs of 

 the other Acephala. 



Reference has already been made to the so-called 

 " shell-gland " which occurs so extensively amongst the 

 Mollusca. That the homologue of this characteristic 

 organ may be found in the " foot-gland " or " fixation- 

 gland " of Loxosoma there can, I think, be no doubt ; and 

 if so, we have here another of the essential features of the 

 Molluscan organization amongst the Polyzoa. 



If we take the evidence of embryology on this question, 

 we find a remarkable agreement between the larvae of the 

 Brachiopoda and Polyzoa"^, also between the primitive 

 form of the latter (as demonstrated by Barrois) and that 

 of the Molluscan group {trochosphere of Ray Lankester) . 

 The " general resemblance " between the larvae of the 

 Entoproda and the Rotifera, on the strength of which 

 Barrois is inclined to believe in an intimate relationship 

 between the Polyzoa and the latter, will hardly weigh 

 against the positive evidence of their Molluscan affinities. 

 The adult forms of the two classes are essentially distinct. 



On the grounds thus briefly indicated, which may be 

 summed up in the proposition that the most charac- 

 teristic organs of the Mollusca have a place amongst 

 the Polyzoa, these two groups, it seems to me, should 

 remain in one and the same subkingdom. I quite 

 agree with Prof. Lankester that the subgroup of the 

 Molluscoida is superfluous. The Polyzoa, in spite of 

 adaptive changes, are, like the Brachiopoda, to which 

 they are most nearly related, of the true Molluscan race. 



* "Les larves de Terebratiile et Terebratuline presentent done reellement 

 line ressemblance etonuante avee la forme primitive dcs Bryozoaires." 

 — Bauhois. 



