326 DR- S- J- HICKSON— EEVISION OE THE 



such structure in any of the numerous Gorgonidse he had examined (Isis, Gorgonia, 

 Sclerogorgia, &c.) ; but I was wrong in placing too much reliance on von Koch's work, 

 as he failed to note in a monograph on the anatomy of the genus the well-marked 

 siphonoglyphe of TuUpora. Ever since the publication of my paper in the ' Philo- 

 sophical Transactions ' von Koch has not brought forward one word of criticism upon 

 my system of classification that requires an answer, and I can only say now that 1 am 

 exceedingly sorry that he should have thought it necessary to make such a personal 

 attack upon me. 



Viguier (35), in a valuable paper on a very remarkable Alcyonarian, Fascicularia 

 edwardsi, in which a number of small AlcyoniumASke colonies are connected together 

 by expansions of the coenenchym, remarks : — " Je ne parlerai pas, au cours de cette 

 discussion, de la classification proposee par Hickson, dans le memoire cite plus haut. 

 En voulant separer d'une maniere aussi absolue les types oii la multiplication se fait par 

 bourgeons naissant dh-ectement sur les polypes, de ceux oii elle se fait par I'inter- 

 mediaire de stolons, cette classification, justement critiquee par Koch a un autre point 

 de vue, avait deja, au moment oii elle a ete proposee, I'inconvenient de laisser en dehors 

 le Paralcyonium, oii les deux modes se trouvent reunis." 



Viguier's argument would be perfectly conclusive if my group Stolonifera were based 

 entirely on the mode of origin of the young polypes. I was probably wrong in assuming 

 that there was sufficient evidence to lead us to believe that in the majority of 

 Alcyonaria they are formed by budding directly from the first-formed polypes ; in fact, 

 it seems to be more probable now that in all the Alcyonaria, except, perhaps, the 

 Pennatulida, the buds are formed in the coenosarcal canals, which connect the 

 ccelentera of the older polypes. The essential feature of the Stolonifera, a feature in 

 which the genera of the group diff'er from all the other Alcyonaria, is that the polypes 

 arise independently from a creeping basal stolon or (in Tuhipora, in Clavularia viridis, 

 and the fossil Sijringopora) also from horizontal platforms or connecting-tubes ; and 

 their walls never become fused or cemented together by a growth of the mesoderm 

 during the whole life of the colony. 



The growth of the colony of a Stoloniferan usually takes place at the periphery of 

 the stolon, that is to say it increases in size horizontally ; the only exceptions to this 

 rule being found in the forms just mentioned, where there is a very considerable 

 vertical growth, and new polypes are formed above the plane of the stolon. In all the 

 other Alcyonaria there is, after the youngest stages, very little basal horizontal growth, 

 but a very considerable distal vertical growth and multiplication by gemmation from 

 peripheral canals. 



The important difi"erences of the mode of growth of the five suborders of the 



Alcyonaria may be seen at a glance by reference to the diagrammatic figures here given. 



It was naturally expected that the authors of the volume on the Alcyonaria of the 



'Challenger' expedition (30) would take the trouble to consider and discuss the 



J 



