THE BRITISH FOSSIL BRACHIOPODA. 309 



Affinities of the Buachiopoda. 



Before describing the soft parts of the adult Brachiopod it will be desirable to say a 

 few words with respect to the position and affinities of the Brachiopoda, as these have 

 been chiefly drawn up from embryological considerations. 



Milne Edwards some years back separated the Mollusca into two divisions, Mollusca 

 and Molluscoidea, and in the last division he placed the Brachiopoda, Polyzoa, and 

 Tunicata, an arrangement that has been followed by many naturalists. 



Although the greater number of zoologists have admitted the close connection of the 

 Polyzoa and the Brachiopoda, some considerable doubt has been expressed with respect 

 to the affinities and position of the latter to the Tunicata ; moreover, strenuous efforts have 

 been made by such excellent observers as Japetus Steenstrup, Morse, Kowalevsky, A. 

 Agassiz, and others, to demonstrate that the affinities of the Brachiopoda and Polyzoa are 

 with the worms, and that they should form a division or two divisions of the Annulosa, 

 and be placed close to the Annelidas. In his review of Kowalevsky's admirable memoir 

 on the embryology of Argiope, Thecidium, and Teredratula, Alex. Agassiz observes ■} 

 " The close relationship between the Brachiopoda and the Bryozoa (Polyzoa) cannot 

 be more fully demonstrated than by the beautiful drawings on pi. v of Kowalevsky's 

 History of Thecidium. We shall now have at least a rational explanation of the homo- 

 logies of the Brachiopoda ; and the transition between such types as Pedicellina and 

 Membranipora and other incrusting Bryozoa is really explained from the embryology of 

 Thecidium. In fact, all incrusting Bryozoa are only communities of Brachiopods, the 

 valves of which are continuous and soldered together, the flat valve forming a united 

 floor, while the convex valve does not cover the ventral valve but leaves an opening more 

 or less ornamented for the extension of the Lophophore." 



I do not know, however, how far Prof. A. Agassiz is justified in stating that 

 Kowalevsky admits the close affinity of the Brachiopoda and Polyzoa, for it is stated 

 in MM. Oehlert and Deniker's analysis of the Russian author's work : — " Let us 

 first consider the Polyzoa. The works of Nitsche, Claparede, Mestchnikoff, Schneider, 

 Uljanin, and Kowalevsky show that these last-named animals are very different from 

 the larvae of Brachiopods ; nevertheless the family of the Pedicellina^, to which the genus 

 Loxosoina is attached, displays some affinities towards them. The larva of Loxosoma, 

 which is in effect formed, as the larva of Brachiopoda, of three segments of which one 

 bears the double fold of the mantle, is fixed in a similar manner by its caudal segment, 

 which is afterwards transformed into a peduncle. But the family of Pedicellinse is 

 still too little studied and the dissimilarities of the Brachiopoda with the other Polyzoa 

 are so marked that it seems difficult to establish, as Huxley desires it, a parentage 

 between these two types." Miss A. Crane, a zealous naturalist, who has given some 

 Silliman's 'American Journal of Science and Art,' 3 series, vol. viii, p. 4/1, for 1874. 



