Sponges frotn the Atlantic Ocean. 323 



form ones may be considered as ** incomplete development." 

 (If there is one thin^ more to be deprecated than anotlu-r in 

 the description of spon;^es, it is the H^urini^ of exceptional 

 forms of spicules as clianicteristic of the species.) 



There is, however, a great diversity of form in all three 

 kinds of spicules, since the terminal inflation of the large 

 spicule is not only occasionally double, and that of the cen- 

 trally inflated spicule- also, but the extremities of the latter, 

 although always more or less iissurate or spined, arc equally 

 varied. 



Then, again, the vertieillatelys]nned and moniliform s]iicules 

 vary in size from 2- to 2()-18(>()tlis incli in length, while tiie 

 absence of any particular form of flcsh-spicule may be sup- 

 plied by the smallest verticillatc ones, in which the central 

 inflation then causes them very much to resemble the centrally 

 inflated flesh-spicule of llalichoudria sidierea and //. JicuSj 

 Johnst., Suben'tea domuncidd, 8dt. (Dr. Bowcrbank, op. cit. 

 vol. ii. p. 202, is wrong in restricting the presence of these 

 centrally inflated flesh-spicules to Jl.Jicus, inasmuch as they 

 are equally present in both the type specimens of H. siiberea 

 and II. ficus respectively, of the Johnstonian collection in the 

 British Museum.) 



The only ap])roach in form to the centrally inflated subske- 

 leton-spicule with fissurate ends of I/i/meraphia verticillata, 

 that I know of, is in llalicnema patera, Bk. (vol. iii. pi. xv. 

 figs. 31 and 32); but hei'e the ends are shai-p -pointed, although 

 the centre of the shaft is once and sometimes twice inflated ; 

 still these spicules are congregated round the great sub-pinlike 

 acuates of the fringe at the circumference of JI. patera, where 

 they thus bear the same relation to each other that the cen- 

 trally inflated spicules do to the great sub-pinlike spicule in 

 Jlynieraphia verticillata. The double terminal inflation of the 

 latter, too, is common in llalicnema patera, while the staple 

 spicule of the body generally, which is smaller, consists of a 

 curved acerate, inflated in the centre, and thickly (althougli 

 not verticillately as in If jmeraphia verticillata) spined througii- 

 out. So that the spiculc-complement of llalicnema patera 

 comes nearest of all known sponges to that of llymeraphia 

 verticillata ; and the former I have thought best for the present 

 to place among the Suberitida. Perhaps llalicnema patera 

 and its like may have to come there also. 



It has been above stated, conjectural ly, that the great sub- 

 pinlike-spiculc which ])rojects from the summit of the aeulca- 

 tion is about 2U(V1800ths inch long (that is, -},- inch) ; but as 

 this spicule from its extreme length is generally broken off" 

 ju.st outside the summit of each aculeation, while its inner 



