181 



retractile ". Under this category he placed the following species : 1. tioJnUs, 

 I. dicliotoma, 1. ocliracea and 1. /lippuris: In 1786 Ellis and Solander, in "The 

 Natural History of Many Curious and Uncommon Zoophytes," p. 105, defined 

 the genus in the following terms : " An animal growing in the form of a plant 

 whose stem is stony and jointed ; the joints are furrowed longitudinally and 

 united together in some by a spongy, in others by a horny substance. It is 

 covered over by a soft porous and cellular flesh, full of little mouths from 

 whence the polyps with their claws come forth, through whom the eggs are 

 produced." They also noted the relationship between this genus and the 

 Gorgonids, a relationship based on the presence in both of " the axis, support 

 or bone of the animal " ; the only difference being the presence of joints in that 

 of the genus under consideration, while in the latter the axis is horny through- 

 out. They suggest that the " articulation " of the axis is an adaptation for 

 swaying in the water. Hexing backwards and forwards in the currents, and so 

 minimising the possibilities of fracture. To these eminent naturalists we are 

 also indebted for the first figures of any species of this genus, Tab. 3, figs. 1-5, 

 representing various parts of /. Iiippiirh, Linna?us. The only other species des- 

 cribed by them are /. oclirarca and I. coccbwa. It is also to Ellis and Solander 

 that we are intlebted for the introduction of the terms nodes and internodes ; 

 but it must be noted that these are used to describe the calcareous and horny 

 parts respectively, whereas the converse usage is now adopted. The following 

 is their description: "Axis articulated, calcareous, sparsely branched; the 

 calcareous portion is white, cylindrical and furrowed ; the internodes are black, 

 horny, constricted and attached to the nodes". In 1791 Esper depicted the 

 axis in three fine plates, and gave a good general description of external features. 

 Lamarck, in 1801, placed this group between the Goi'gonacea, with an axis 

 apparently horny, and the " Corail," with an entirely calcareous skeleton. In a 

 later work, published in 1816, he narrowed down the generic distinctions and 

 established a new group, " les Melitees " (genus Melihm). Following this, 

 Lamouroux in the same year established yet another division under the name 

 of " les Mopses " (genus Mopsea) ; and at the same time united the three under 

 " I'ordre des Isid(^es," i.e., " tous les Coralliaires dont I'axe est articule ". This 

 innovation was not accepted by Blainville in 1834 (XVI.), but was adopted by 

 Ehrenberg 1834 (XVII. ), Lamarck 1836 (XIL), Dana 1846 (XIX.), and Milne- 

 Edwards and Haime in subsequent works (XX., XXI. and XXII.). 

 The classification would thus appear as follows : — 



(1) the calca- 



Isidinte, with an 

 axis which bears 

 internodes 



' (a) hoi'ny in appearance. 

 Branches borne on 



reous nodes = Ittis. 

 (2) the horny 



internodes = Mopsea. 



. (b) of a suberous appearance . . = Melitwa. 



