310 GENERAL SUMMARY TO 



regard the group Mollusca as a single series, with the Polyzoa at the bottom and the 

 higher forms at the top, nor does he accept the division of the group into Mollusca and 

 Molluscoidea, but divides it into two branches, the Eucephala and the Lipocephala, and 

 in the second branch he places the Polyzoa, Brachiopoda, and Lamellibranchiata. 1 



Finally we have the extreme view of Morse, that " the Brachiopoda are not merely 

 related to the Vermes, but are actually ancient cephalized Chaetopod Annelids." Packard 

 in his ' Life Histories,' 1876, gives a still different opinion. He says, p. 149, " It will be 

 seen that neither in the Polyzoa nor Brachiopoda are there any true Molluscan characters, 

 nothing homologous with the foot, the shell-gland, or the odontophore. The Brachiopods 

 should in our opinion, be perhaps united with the Polyzoa and form a group lower but 

 sub-parallel with the Annelids. The Brachiopods, from the facts afforded by Morse 

 and others, have neither such a nervous system of respiratory or circulatory organs, nor 

 annulated body, as would warrant their union with the Chaetopods. Morse has fully 

 proved that they are a synthetic type, combining the features of different groups of 

 Worms, and this fact apparently forbids their being regarded as a group of Chaetopods. 

 Looking at the subject from an evolutional point of view, we should be inclined to regard 

 the Brachiopods and Polyzoa as derived from common low vermian ancestors, while the 

 Chaetopod Worms probably sprang independently from a higher ancestry." 



I regret not to have space to reproduce Prof. Brooks' instructive reasoning upon the 

 subject ; he says, at p. 93 of his Memoir : " Our account of the organisation of the Lingula 

 larva shows that it is not only like a Polyzoon, but that it is actually one ;" and at p. 102 

 he adds : " The Brachiopoda then are ' Vermes ' in the same sense that the Echinoderms, 

 Molluscs, Tunicates, and Vertebrates are, and in order to include them we must make the 

 word almost synonymous with ' Ccelomatous Metazoa.' In the case of the Brachiopoda 

 and Polyzoa, on the other hand, we have a resemblance which is definite and minute, 

 which is most marked during the youngest stages of development and gradually becomes 

 less conspicuous as the adult characteristics are acquired ; and there appears to be every 

 reason to conclude that the relation of the Brachiopoda to other Invertebrates must be 

 traced only through the Polyzoa." In conclusion, he says, p. 106, "The Rotifera, 

 Polyzoa, and Veliger, seem to be three branches which diverged, very early, from a 

 common Vermian stem. The Brachiopoda are the most highly specialised representatives 

 of the Polyzoon branch, and the true Mollusca stand in a similar relation to the Veliger 

 branch. The three stems appear to be sufficiently closely related to each other, and 

 sufficiently sharply distinguished from all other animals to constitute by themselves one 

 of the fundamental divisions of the Animal Kingdom, which might be called, on account 

 of the conspicuous character of the trochal disk, the Trochifera." In conclusion, he adds, 

 " I may be allowed to call attention to the obvious fact that the persistence of Lingula, 

 entirely without change, for a period which is too great to be measured in the terms of 



1 "Note on Embryology and Classification," 'Quart. Journ. of Microscopical Soc.,' vol. xvii (New 

 Series), p. 448, October, 1877. 



