464 Mr Gardiner, Notes on Variation, 



as new under the name of F. variabile 1 — and Blastotrochus nutrix 2 . 

 The latter genus is one which I can consider as in no way different 

 from Flabelkim. It was founded by Milne-Edwards and Hamie 3 

 on a misconception, the universal belief at that day and in 

 Semper's time being that the coral skeleton was formed by the 

 endoderm, whereas it is really a deposit outside the ectoderm and 

 hence morphologically completely outside the coral polyps. The 

 wall of the coral of Flabellum is epitheca and not theca, so that 

 hence there is no polyp tissue external to it, from which budding 

 could occur. 



The Cape of Good Hope specimens belong to F. rubrum, but 

 have about 2 per cent, of their number intermediate towards 

 F. stokesi and F. nutrix. The Maldive specimens mostly belong to 

 Semper's F. stokesi, but some to the same author's other species. 

 The first three cj^cles of septa in all are equal and fuse in the 

 axial fossa by trabeculae from their edges. The fourth cycle is 

 smaller, but commonly some of its septa fuse to the others by 

 trabeculae, this character being generally more marked in F. stokesi. 

 The Maldive specimens of each of the so-called species as com- 

 pared with the Cape specimens show an increased length of the 

 basal scar. The breaking off of the corallum takes place along 

 one of the lines of growth, and probably the growth is greater 

 with increase of temperature, better food-supply, etc., so that even 

 if all corallites broke off along the same growth line — an unlikely 

 supposition — the scar would in different regions vary in size. 

 There is absolutely no difference in the polyp anatomies of either 

 of the two species, but the presence of wings along the end of 

 the calicle in one and of spines in the other is a fairly definite 

 difference. The British Museum forms show, however, inter- 

 mediates in this character and also in the size of the scar. Out 

 of about 600 the total number of intermediates (in the strictest 

 sense) was 17, of which 4 alone were intermediate in both 

 characters. It is hence evident that F. rubrum and F. stokesi re- 

 present variations of the same species. 



Doubt only remains as to the so-called Blastrotrochus nutrix. 

 I had only one specimen from the Maldive, which was absolutely 

 identical with Semper's description of the species. It was quite 

 similar in the polyp anatomy to the other forms, but in the 

 corallum closely approached to F. rubrum. The so-called buds 

 are approached in many of the Cape specimens of F. rubrum. 

 Neither in these nor in the Maldive specimen is there any 

 connection with the tissues of the large polyp, and it is doubtful 

 whether they may not have been largely derived from ova, rather 



1 Loc. cit. pp. 245—251. 



2 Loc. cit. pp. 237—241. 



3 Ann. des Sc. nat., 3 e s6r., t. ix., p. 281 (1848), and Cor. n. p. 87 (1857). 



