a single colony, too much stress cannot be laid upon the buds, the number of which may 

 depend on the season of the year or on the condition of sexual maturity of the zooids. 



The descriptions of C. dodecalophus which have previously been published were drawn 

 up in the absence of all information relating to other species of the genus; and until this 

 information was forthcoming it was of course impossible to decide which of the characters were 

 of specific rather than of generic value. It may, however, be remarked that the specific name 

 given by M'Intosh proves to have been well chosen ; since, as I believe, the number of arms 

 is a character of specific value. 



The systematic position which Cephalodiscus and Rhahdoplejwa appear to occupy is 

 indicated by the following classification. 



HEMICHORDATA ■). 



Bateson (Quart. J. Micr. Sci. XXV, Suppl., 1885, p. iit). 



Order i. ENTEROPNEUSTA Gegenbaur. 



Order 2. PTEROBRANGHIA Lankester. 



(Quart. J. Micr. Sci. XVII, 1877, p. 448). 



= ASPIDOPHORA Allman. 

 (J. Linn. Soc. Zool. XIV, 1879, pp. 490 n., 586). 



= BRACHYSCOLECIDA BRANCHIATA Ehlers (90, p. 173). 

 = CEPHALODISCIDA + RHABDOPLEURIDA Fowler (92, 2). 



Earn. I. Cephalodiscidae. 



= Enteropneusta Monobranchiata Schimkewitsch (93, p. 238). 



Cephalodiscus M'Intosh (82). 



Earn. 2. Rhabdopleuridae. 



Rhabdopleura Allman. 

 (Quart. J. ViXcx. Sci., IX, 1869, p. 57; Rep. Brit. Ass. (1868) 1869, p. 311). 



? Order 3. PHORONIDEA. 

 Phoronis Str. Wright. 



i) Numerous other names, such as Pharyngopneusta, Archicoelomata, Trimetamera, Archichorda, Diplochorda, Protochordata, 

 Adelochordata, "Urchordaten", "Axobranches", "Vermidiens", "Procoides", Branchiotrema, Hydrotrema, have been used as the equivalent 

 of Hemichordata, or of this group in addition to others, or of its subdivisions. These terms ai'e for the most part dealt with historically 

 l>y DE Selys I.ongchamps (04, pp. 102 f.). Reference may also be made to Delage .md HliROUAKD (97, 98) .ind to Willey (99). 



