50 AMERICAN JOURNAL 



In this connection it may not be unfair to quote Prof. Morse 

 himself: "We find (in Lingula) the intestine also running paral- 

 lel with the sides of the body, at its posterior portion becoming 

 convoluted and terminating on the right side, the straight part 

 producing a curve arching toward the haemal valve and sur- 

 mounted by a heart as we witness in most Lamellibranchiata, 

 showing clearly in this view alone its homological identity with 

 the Lamellibranchiata. The limits of this paper will not allow 

 us to carry homologies from this point to the other two classes 

 of Mollusca, and in fact it would be hardly necessary to do so, 

 as the path is rendered apparent and plain through the medium 

 of Lamellibranchiates." While no one will deny to naturalists 

 the right to modify their opinions on the development of new 

 facts in science, it seems strange that, after pointing out the 

 obvious homologies of two groups so forcibly as in the paragraph 

 I have just quoted (Proc. Boston Soc. Nat. Hist, ix, p. 60, 

 1862), the gentleman in question should turn his back on his 

 expressed opinions, while the facts still remain undeniable and 

 undisputed. 



I shall not hope to succeed in or even to essay the definition 

 of the type which essentially corresponds to the Articulata of 

 Cuvier, which has defied the best efforts of the most eminent 

 naturalists. It might almost be said that they are characterized 

 by diversity in the development of special features of structure, 

 with a marked tendency to the repetition of similar organs or 

 groups of organs antero-posteriorly, in bilateral symmetry. 

 This diversity exhibits itself no less in the distinct classes than 

 in the entire group of animals. The different subdivisions are 

 united by features which are more or less characteristic of small 

 groups, which at the same time present vestiges of other charac- 

 ters, which are typical of other small groups, and so the fre- 

 quently interrupted threads of affinity, though binding the mass 

 more or less completely together, nevertheless exhibit a notable 

 want of continuity. 



I trust I shall not be accused of undue attachment to broken 

 idols when I remark that the group Annuloida of Huxley ap- 

 pears to me to be heterogeneous and unsatisfactory. With the 

 exception of the Echinoderms, it might advantageously be com- 

 bined with the Annulosa without violence to their affinities. 



We now come to the Annelids, the group to which Prof. Morse 



being; able to remove it from the group (Tuvicata) to which it belongs?" 

 And also, "If we suppress in the lamellibranchiate Acephalan the foot 

 and the pedal ganglia, there remains an organism having the greatest 

 analogy with that of the Brachiopod, always excepting the position of 

 the valves." 



