1 7 ^ 
Note on the Evolution of Species within the Genus. 
In considering the relationships between the various species of Siphonogorgia, it seems 
probable that the presence of a large number of small spicules in the points of the anthocodise 
is more primitive than a smaller number of large spicules. Similarly, a crown composed of many 
rows of slender spicules, is probably a more primitive condition than a crown with only a few 
rows of heavy spicules. The most primitive type of crown is not however always to be found 
associated with the most primitive type of points, nor the least primitive crown with the 
least primitive points. Thus S', media is an example of a species with one pair of clearly 
defined spicules in the points, but the crown may extend to twelve rows. On the other hand, 
S. cylindrata has primitive points of three to four pairs of spicules and a crown of only 
three to four rows. The most primitive forms as regards anthocodial armature are distinctly 
in the minority. 
If we interpret the most specialised forms of anthocodise as having three to six rows in 
the crown, and one pair of principal spicules in the points, S'. asper'ula , 5 . jlavocapitata , 
S'. hicksoni (Harr.), S. niacrospiculata , S. mirabilis , and S. robusta all lie between these limits, 
while S'. dojleini is the only species with twelve rows in the crown and four pairs in the 
points. No forms have been previously described even with so many as eight rows in the crown, 
and three to four pairs in the points; but such occur amongst the specimens from the Siboga 
Expedition, viz., S'. eminens Chalmers, and S. simplex Chalmers. 
The view suggested is that a trend of evolution in species of Siphonogorgia has been 
(i) towards a reduction of the number of spindles in the points, two hockey-clubs being best 
of all; and (2) towards a reduction of the number of rows of horizontal spindles in the crown, three 
or four rows being probably an optimum. It may be that a reduction in the number of spicules 
in the crown and points implies more effective movement of the anthocodise, effective as regards 
rapid retraction from stimuli and as regards rapid capture of nutritive particles or organisms. 
Other lines of utilitarian evolution may perhaps be discerned in verrucse, branching, solidity 
and so forth. 
* 
Genus Scleronephthya. 
The genus Scleronephthya includes Nephthyids without supporting bundle, with thick 
canal-walls thickly supported by spicules, with polyps singly or in bundles, and with hints of an 
irregular internal axis in the stem formed of compacted spicules. 
The terminal portions of -the variously branched stem are thickly covered with polyps. 
The mouth of the polyp is covered by eight points of spicules in chevron, continued on to the 
bases of the tentacles, with a more or less pronounced crown or basal collaret, the distinctness 
of which depends largely on the state of contraction. The spicules include large and small, 
straight and bent, strongly tuberculate spindles. 
The known species are S'. pustulosa W. and S. and 5 . flexilis Thomson and Simpson. 
To this genus we transfer 5 . crassa (= Paraspongodes crassa Kuk.) and must add S', flexilis , 
var. compacta. The following contrast may be indicated : 
