GENERAL CONSIDERATIONS ON THE MOLLUSCOIDA. 85 



(No. 8). These two authors are inclined to claim for the Sipun- 

 culidae also affinity to these groups. A similar view has recently 

 been adopted by EHLERS (No. 3) and ROULE (No. 12), the latter 

 regarding the Brachiopoda, the Bryozoa, and the Phoronidae as a 

 sub-group of the " Trochozoaires monomeriques," and suggesting 

 distant relationship to the Sipunculidae, the Molluscs, and the 

 Rotifera. ROULE lays special stress on the Trochophoran characters 

 of the Molluscoid larva. We ourselves have adopted the view of 

 HATSCHEK (No. 6), who groups together the Phoronidae, the Bryozoa, 

 and the Brachiopoda as Molluscoida, but excludes the Sipunculidae 

 from the group. From all that is as yet known about the Ento- 

 procta, we would, with HATSCHEK, separate them also from the 

 Bryozoa and the Molluscoida generally. Further, according to the 

 more recent researches made by MC!NTOSH, HARMER (No. 10), 

 SPENGEL (No. 13), and EHLERS (No. 3) in connection with CepJialo- 

 discus, and by FOWLER (No. 4) in connection with Rhdbdopleura, 

 these forms also must be removed from the group of the Molluscoida 

 and probably grouped, as sedentary Enteropneusta, with Balano- 





The union of the Phoronidae, the Bryozoa, and the Brachiopoda 

 to form a sub-group rests chiefly on the structural resemblance of 

 the adult forms. We have already repeatedly pointed out anatomical 

 features possessed in common by these forms, and refer the reader 

 to the diagrams given in Figs. 5 (p. 9), 28 (p. 57), and 41 (p. 80), 

 which, when compared, reveal so uniform a fundamental type that 

 we can only refer the agreement in structure found here to homology. 

 The Molluscoida are provided with a true coelom, a body-cavity lined 

 with a flattened epithelium which is often ciliated, and in which the 

 intestine is suspended by mesenteries (these, in the Phylactolaemata, 

 being replaced by the funiculus). Only in the Gymnolaemata is the 

 lining of the body-cavity no longer epithelial, while strands of con- 

 nective tissue traverse the so-called funicular tissue of the body-cavity. 

 The dorsal region of the body appears shortened, the oral and anal 

 apertures of the looped alimentary canal are consequently approxi- 

 mated, as is so often the case in tubicolous animals or those leading 



* [MASTERMAN'S interpretation of Actinotrocha, if correct, shows that Phoronis 

 must for the future be associated with Oephalodiscus and Rhabdopleura. It 

 is now fairly well established that these genera are closely related with Balano- 

 glossus to the primitive chordate stock, and have no affinities whatever to the 

 Molluscoida. HARMER, who has worked at the development both of the Ento- 

 and Ectoproctous Bryozoa, still retains them in one group and considers that 

 they have no affinities with Phoronis. See HARMER and PROUHO, Appendix 

 to Literature of Ectoprocta, Nos. III. and V. ED.] 



