ON THE DIPLOCHOFIDA. 715 



On the Diplocliorda.' 



IV. On the Central Complex of Ceplialodiscus 

 dodecalophus, McI. 



By 

 A. T. Masti'i-iiiaii, M.A., D.)!»c., 



LecUiicf oil Z')u\i)<^y, 8ciiool ut' Aleiliciiic, Eiiiiilniigh. 



Willi Plates 32 ;uid 33. 



Introduction. 



In the following' description a number ut" the organs involved 

 already possess a plurality of uames^ arising from the fact 

 that various observers liave recognised differing- homologies, 

 and emphasised them in the nomenclature. Thus the "buccal 

 shield" of Cephalodiscu s is also commonly termed the 

 ^' epistome/' "oral disc/' and " pre-oral lobe." In the case of 

 the two canals opening from the cavity of the buccal shield to 

 the exterior there is the same difficulty. From homolog}' with 

 Balanoglossus they are termed the " proboscis pores," 

 although the buccal shieldhas never been termed theproboscis; 

 and they are more than pores, being of the nature of definite 

 canals. As this work indicates an even closer structural 

 resemblance to Balanoi>'lossus than heretofore recoR-niised, 

 it would be well to retain as far as possible the nomenclature 

 indicating this relationship; hence the terms collar cavities 

 and trunk cavities are retained, whilst the term pre-oral canal 

 is used as a synonym of proboscis pore with its attendant 

 canal. The term subueural gland is retained for the " uoto- 

 ' Read before llic lloyal Society of Ediuljurgli, Mny, I'JUl. 



