Simpson — A Revision of (he Gorgonellidae. 53 



(3) The thickness of the eoenenchyma in the main stem is seldom as 



great as in the branches or twigs, and is usually from 0-75 to O'o 



times its thickness. 



Bearing these facts in mind, let us see if any inference may be made as 



to the mode of growth, and also as to the possibiUty of these apparently 



diverse forms being i-eferable to a single species. 



(1) We find that what obtains with regard to the various measurements 



in different parts of the same colony also holds good in the 

 corresponding parts of colonies of ditl'erent sizes. 



(2) It is also obvious tliat increase in thickness in the older parts of a 



colony is due, not to increase of thickness in the eoenenchyma, 

 but to increase in the diameter of the axis. 



(3) Increase in length in the younger branches and twigs is not propor- 



tional to increase in the thickness of the eoenenchyma, but tends 

 rather to the reverse of this situation. 



We are therefore in a position to conclude that increase in tiie thickness 

 of the eoenenchyma is not proportionate to the age of the colony, but that 

 the eoenenchyma attains to its typical thickness at a very early stage, and 

 that further elongation and consequent thickness are caused more by the 

 gtowth of the axis than the eoenenchyma ; or, in other words, the earlier 

 period of growth consists chiefly in development of the eoenenchyma, while 

 the strengthening of the axis and elongation of the colony come at a later 

 period. Consequently the younger colonies are more bushy and fleshy, and 

 the older colonies have proportionately a greater amount of axis, and are 

 therefore more rigid. 



The distribution of the polyps, the nature of the verrucae, and the 

 details of the canal-system are exactly similar to those described for the 

 protruding verrucae \a.\\Qiy oi JunccUa juncea. Figs. 18 an<l 10 have been 

 added to show the leading characteristics; and these should be compared 

 with the corresponding figures (12 and 13) of J.juncea. 



Colour. — The great majority of the specimens examined in this species 

 are of a dai'k brick-red colour; but tlie following tints also occur: — 

 (1) reddish orange, (2) brownisii yellow, (3) orange-yellow, (4) lemon, and 

 (5) creamy-white. There is thus almost a series of gradations from white 

 through orange to red. 



Spicules of J. gemmacea. 



The spicules of this species, as lias already been pointed out, are identical 

 both in types and measurements with those oi J.juncea, so that the description 

 and measurements given for the latter may be taken as typical. 



