BRACHIOPODA. 263 



shewn in fig. 137, is post-oral, and not prce-oral. The ring of tentacles is like 

 the ring in Actinotrocha (the larva of Phoronis) amongst the Gephyrea. 

 Although there is no doubt a striking resemblance between the tentacular 

 disc of a larval Brachiopod and the lophophore of a Polyzoon, which has 

 been pointed out by Lankester, Morse, Brooks, etc., their hornology is 

 rendered, to my mind, very doubtful (1) by the fact that the lophophore is 

 prre-oral in Polyzoa 1 and post-oral in Brachiopoda; and (2) by the fact that 

 the concave side of the lophophore is turned in nearly opposite directions 

 in the two forms. In Brachiopods it is turned dorsalwards, and in 

 phylactola?rnatous Polyzoa ventralwards. 



The view of Morse, that the Brachiopoda are degraded tubicolous 

 Chaetopods, is not so far supported by any definite embryological facts. 

 The development of the tentacular ring as well as its innervatiou from the 

 sub-cesophageal ganglion prohibit us, as has been pointed out by Gegenbaur, 

 from comparing it with the tentacles of tubicolous Chsetopoda. 



BIBLIOGRAPHY. 



(^2S) W. K. Brooks. "Development of Lingula." Chesapeake Zoological Labo- 

 ratory, Scientific Results of the Session of 1878. Baltimore, J. Murphy and Co. 



(326) A. Kowalevsky. "Development of the Brachiopoda." Protocol of the 

 First Session of the United Sections of Anatomy, Physiology, and Comparative Anatomy 

 at the Meeting of Russian Naturalists in Kasan, 1873. (Eussiau. ) 



(327) H. Lacaze Duthiers. "Histoire de la The"cidie." Ann. Scien. Nat. etc. 

 Ser. 4~, Vol. xv. 1861. 



(328) Morse. "On the Early Stages of Terebratulina septentrionalis." Mem. 

 Boaion Soc. Nat. History, Vol. n. 1869, also Ann. & Mag. of Nat. Hist., Series 4, Vol. viu. 



1871. 



( 320 j _ "On the Embryology of Terebratulina." Mem. Boston Soc. Nat. 



History, Vol. in., 1873. 



(330) "On the Systematic Position of the Brachiopoda." Proceedings of the 



Boston Soc. of Nat. Hist., 1873. 



(331) Fritz Miiller. " Beschreibung einer Brachiopoden Larve." Midler's 

 Archiv, 1860. 



1 For the ectoproctous Polyzoa it might be held that the ciliated ring of tentacles is 

 post-oral, but the facts of development recorded in the previous chapter appear to me to 

 shew that this view is untenable. 



