REPORT ON THE DEEP-SEA MEDUSAE. xv 



and organs of sense. To the Scyphopolyps belong : (a) the real ancestral form of the 

 Acraspedse (Scyphostoma) ; (b) the hypothetic ancestral forms of the corals (Procoral- 

 lium) ; (c) Scyphopolyps, which are probably propagated as such without Medusa formation 

 (Spongicola, Stephanoscyphus). Class II. Corals {Corolla, or Anthozoa) is phylogenetically 

 derivable from the Scyphopolyps (ProcoraUimri), probably a polyphyletic group (having 

 arisen at different times from several different groups of the latter). Class III. Medusae is 

 most probably polyphyletic ; the section of the Craspedotae has likely arisen from several 

 groups of Hydropolyps (Polyphyletic, § 11), but the section of the Acraspedse from a 

 single group of Scyphopolyps (Monophyletic, § 14). Class IV. Ctenophora is probably 

 monophyletic, having proceeded from a group of Anthomedusae (Cladonemidae) (Ctenaria, 

 System, p. 107). Class V. Siphonophora is probably polyphyletic, having proceeded from 

 several forms of Anthomedusas (Codonidse, Sarsiadae, System, pp. 14, 20, &c). The 

 Siphonophora are polymorphic Medusae cormi or colonies, whose associated personae have 

 become differentiated by division of labour, and assumed very different forms. 



§ 19. Ectocarp and endocarp Medusas. As the Craspedotse are more widely separated 

 by the foregoing distinctions (above all by the absence of the gastral filaments and by 

 the ectodermal genitalia), it is proposed to dissolve the class of Medusae entirely, and to 

 divide the whole tribe of the Acalephse or Cnidarise into two principal groups, of which 

 one (Ectocarpse) includes the groups just mentioned, the other (Endocarpse) the Acras- 

 pedse, the Scyphopolyps, and the Corals (with gastral filaments and with endodermal 

 genitalia). This proposition seems entirely justified from a phylogenetic point of view, 

 and we would accept it unconditionally, if we were in a position to carry out a 

 phylogenetic system of the Cnidarise completely and with certainty. Unfortunately, this 

 is not the case at present. The most probable admission at present is, that the ancestral 

 group of the Acalephse (the primitive polyps, Archydras, § 18) were early split up into 

 the two diverging tribes of the ectocaqD Hydropolyps (without taaniola) and the endocarp 

 Scyphopolyps (with taeniola). The Craspedotse (with the later side branches the 

 Ctenophora and Siphonophora) issued from the former, the Acraspedae and Anthozoa 

 (Corals) from the latter. Only, as, moreover, a polyphyletic origin has now become 

 more probable for the majority of the said classes of Cnidarise, it seems more accurate 

 for the sharp definition of these classes and their logical arrangement, to abandon at pre- 

 sent carrying out a phylogenetic system and to define the said five classes to the extent 

 known : — (1) Polypi, (2) Medusse, (3) Siphonophora, (4) Ctenophora, (5) Coralla, If, 

 on the other hand, we prefer to take their phylogenetic conditions as the fundamental 

 plan of their systematic classification, it would be carried out according to the following- 

 table : — 



