LABECHID.E. 335 



is corneous. During the course of growth the primitive disc 

 of Labechia is increased in thickness by the addition of suc- 

 cessive thin strata, which closely conform to the subjacent 

 fundamental crust, being elevated where the spines are situ- 

 ated. As these successive layers leave a small space between 

 them, and are in themselves very thin, they give rise to a false 

 appearance of tabulae." 



Apart from the fact that our present knowledge of the minute 

 structure of Labechia will not allow us to accept the above 

 account of the development of the skeleton as entirely correct, 

 there are certain general considerations which preclude an 

 unhesitating acceptance of the Hydractinian affinities of the 

 genus. The most important of these considerations are, in 

 the first place, that the skeleton of Hydractinia is encrusting, 

 whereas that of Labechia is entirely like that of many corals, 

 and is provided with a basal " epitheca ; " while, secondly, 

 the columns of Labechia are not certainly known to be per- 

 forated at their summits, and there is at present no evidence of 

 the existence of any superficial cells or openings which may be 

 supposed to have given exit to the zooids. 



As we have previously seen, the genus Labechia was referred 

 by Milne-Edwards and Haime to the ChcetetincB, and has been 

 more recently regarded by Professor Martin Duncan as a 

 sub-genus of Montictdipoj'a. It is, indeed, quite clear that if 

 Labechia be a coral at all, then it will find its nearest ally in 

 the MonticuliporidcB, and especially in Fistulipora, M'Coy. 

 From this point of view, it is worth while to glance for a 

 moment at the resemblances presented by Labechia conferta, 

 E. and H., and Fistulip07^a incrassata, Nich., as regards their 

 internal structure. Thus, if we compare the vertical section 

 of these two types (see fig. 44 c, and PI. XV., 3 b) we see 

 that in both the basis or general tissue of the skeleton is made 

 up of a series of lenticular vesicles, traversed at regular inter- 

 vals by the vertical columns in Labechia, and by the tabulate 

 tubes of the large corallites in the Fishdipora. Similarly in 

 tangential sections (PL XV., 4, and PI. XV,, fig. 3 a), we have 



