EEPORT ON THE TETRACTINELLIDA. 
r>3 
nowise disqualifies the specific designation from being used with a new generic name, and 
since, for the last fifty years, it has been continuously employed by a succession of authors 
to designate the same sponge, it is likely to continue to be so employed, unless more cogent 
objections than those alleged by Vosmaer are forthcoming. 
Good accounts of the general characters are given by Johnson and Bowerbank; the 
histology is described in my paper on the species {loc. cit.). Vosmaer found in his 
specimens “ a stronger developed dermal mesodermic layer with smaller subdermal 
cavities ” than I figured in mine, and conjectures that this may be due to a “ difierent 
state of contraction.” The fact I do not doubt, the explanation I do not understand, 
but this is of no consequence as Vosmaer s description explains itself. There is, as he 
truly says, relatively more mesodermal tissue in the outer part of the cortex in his 
specimens than in mine, and consequently the subdermal cavities are smaller; the relative 
abundance of mesoderm is connected with the growth of the sponge, in one sponge there 
may be more, in another less (indeed, in the same individual the cortex may vary from 
the structure shown in Vosmaer’s figure to that represented in mine), and in a young 
sponge there is less than in a fully grown one ; evidently Vosmaer’s specimens were more 
fully grown than mine, which are not more than 10 mm. in diameter. Vosmaer 
complains of my illustrations of this species as being “ diagrammatic,” I take the 
opportunity of explaining that there are no grounds for this charge ; my drawings are 
accurate tracings by “camera lucida,” mere outlines, and very inartistic, no doubt, but 
absolutely faithful, and, after all, on comparing them with Vosmaer’s more finished 
figures, I fail to see that they convey less real information {loc. cit., pi. ii. fig. 10). 
0. Schmidt fell into great confusion with respect to this sponge. One almost doubts 
whether he could ever have seen it, or surely he would not have referred it to Tetilla. 
His genus Craniella is evidently, however, founded on the characters of this species. The 
two shdes of mounted spicules presented by Schmidt to the British Museum as examples 
of Tethya cranium are evidently from two quite different sponges, one from Iceland may 
be Tetilla polyura, the other from Florida some species (not cranium) of Craniella. 
Craniella infrequens (Carter). 
Tethya cranium, var. infrequens, Carter, Ann. and Mag. Nat. Hist., ser. 4, vol. xviii. p. 405, 
pi. xvi. fig. 48, 1876. 
,, „ ,, ,, Norman, Bwk., Mon. Brit. Spong., vol. iv. p. 43, 1882. 
,, ,, „ ,, Hansen, Norske Nord. Exped., Spongiadse, p. 18, pi. v. fig. 5, 
and pi. vii. figs. 17, 18, 1885. 
Sponge similar to Craniella cranium. 
Spicules. — I. Megascleres. 1. Somal oxea. 2. Cortical oxea, 0'58 by 0‘032 mm. 
3. Protrisene, rhabdome 0'032 mm. in diameter; cladi 0‘14 by 0*026 mm., chord 0*16 
mm. 4. Anatrisene, cladi 0*16 by 0*02 mm. chord 0*22 mm. 
