102 ENTOPROCTA. 



(Lehrb. d. Zool., p. 40). Just as surely as the orientation given above seems 

 established for the Entoprocta, does that entirely ditferent interjiretation of the 

 Eetoprocta, sujiported by a comparison with Phoronis, seem justified. In this 

 group the oral and anal apertures are dorsal, the ganglion is supra-oesophageal, 

 and the ring of tentacles is post-oral. The ganglia and the crown of tentacles 

 would thus not be homologous in the two groups. If other divergences of 

 structure be added (tlie want of a body-cavity in the Entoprocta, the position 

 of the anal a^ierture, the characteristic nephridia formed on the type of the 

 head-kidney), sufficient grounds are found for completely separating the Ento- 

 procta from the Eetoprocta. 



We must, however, bear in mind the fact that the foundation 

 upon Avhich the above view of the systematic position of the 

 Entoprocta rests, contains a considerable number of hypothetical 

 elements. Among the decisive reasons for separating the Entoprocta 

 from the Eetoprocta are two observations of a very difficult nature 

 (that of the metamorphosis and that of the structure of the nephridia), 

 and, from these, errors may not altogether have been excluded. 

 Until further corroborating investigations have been made, any 

 attempts to decide the affinities of the Entoprocta must be regarded 

 as provisional. "We liave, therefore, appended them to the Mollus- 

 coida, though as an independent group.* 



LITEEATUEE. 



1. Barrois, J. Memoire sur la Metamorphose de quelques Bryo- 



zoaires. Ann. Set. Nat. (7). Tom. i. 1886. 



2. Ehlers, E. Zur Kenntniss der Pedicellineen. Ahhandl. der 



kgl. Gesellscliaft der Wissenscli. Giittingen. Bd. xxxvi. 1890. 



3. FoETTiNGKR, A. Sur I'Anatomie des Pedicellines de la cote 



d'Ostende. Arcliiv. Biol. Tom. vii. 1887. 



4. Harmer, S. F. On the structure and development of Loxosoma. 



Quart. Journ. Micro. Sci. (2). Vol. xxv. 1885. 



5. Harmer, S. F. On the life history of Pedicellina. Quart. 



Journ. Micro. Sci. (2). Vol. xxvii. 1887. 



* [In the foregoing account of the Brj'ozoa, considerable stress has been laid 

 on the su])posed relationship of the Eetoprocta to Phoronis, and, as a con- 

 sequence, the Eetoprocta are completely severed from the Entoprocta. These 

 conclusions are liy no means accepted Ity all students of the Bryozoa. Harmer 

 (Eetoprocta Lit., No. III.) does not consider that the Eetoprocta have any 

 connection with Phoronis, and he would regard any structural resemblances as 

 the result of coincidence rather tlian of close relationship. Both Harmer and 

 PiiOUHO (Ectojnocta Lit., Xo. VI.) regard the Eetoprocta and the Entoprocta 

 as nearly related. 



An important article dealing with the Bryozoa has recently appeared in 

 Sedgwick's Ted -hook of Zoology (1898). Here the whole question as to the 

 morphology and relationship of the Bryozoa is discussed, and Harmer's con- 

 clusions are adojjted. Important criticisms of our authors' interpretation of the 

 surfaces of the adult and larval Eetoprocta are given. — Ed.] 



