372 .Mr. J I. J. Carter on the Hcxactiiicllidic. 



tlie spicule disappears under the parasitic l)olypc {PaUthna 

 fatxui) which afterwards, for some distance down, cov^ers tlie 

 cord like a bark. Finally, the spicules again make their ap- 

 pearance, but now with the spines gone and the bracket-like 

 processes alone remaining in the form of a rough more or less 

 continuous spiral line round the spicule, which, together with 

 the free extremities of the smooth anchoring-one, also are 

 always broken off, so that their free terminations are gone : this 

 is the state in which these spicules appear for the most part 

 in the trade specimens. 



I have now described the anchoring-spicules of the specimen 

 oi Ilyuloneiaa above mentioned, whose body is about \\ inch 

 long ; and tliroughout the spicule, all the spines and blunt ends 

 of the bracket-like processes both within and without the body 

 are directed upwards — that is, towards the sponge at the summit 

 of the cord. 



Had I not been misled by the observations of others to regard 

 the mounted specimen of the young Holtenia Carpenteri'''- half 

 an inch long " in the first place as a young Hyahnema, the 

 mistake t.) which I have above alluded would not have occm'red. 

 But finding it out, and having therefore had to examine more 

 particularly these anchoring-spicules in an undoubted specimen 

 of llyalonema^ I am enabled not only to correct the error, but 

 to add more authentic information on the subject than was pre- 

 viously possessed, as well as to point out decisive marks for 

 distinguishing between young Tloltenue and young Hyalone- 

 mata another time. 



The transition from the sparsely spinfid anchoring-spicule of 

 Holtenia Carpenteri through that of Meyerina claviformis to 

 that of Hyalonema is represented in PI. XIY. figs. 7, 8, & 9, where 

 also a comparative view of the heads or free terminations of 

 the anchoring-spicules of Laharia hemisplioirica (figs. 1 & 2), 

 Meyerina claviformis (fig. 3), Eiqjlectella (figs. 4 & 5), and 

 Holtenia Carpenteri (tig. 6) is also given, to which I have 

 alluded in the " Observations " appended to my description of 

 Labaria (' Annals,' vol. xi. p. 280, &c., 1873). 



Holtenia Carpenteri^ Pheronema Annte, P. Grayi, and Meye- 

 rina claviformis all probably possess the same kind of birotulate 

 spicule as Hyalonema (PI. XIII. fig. 21). I say "probably " 

 with reference only to Prof. Leidy's hasty description of this 

 sponge, in which this spicule appears to have been overlooked. 

 As in Hyalonema^ so also probably in all the other Hexacti- 

 nellida3 characterized by the birotulate flesh-spicule, this is not 

 unfrequently found in a sexradiate form, which at once iden- 

 tifies it with the rosette (fig. 22) ; tliat is, it may consist of three 

 birotulates joined together in the centre, and thus present six 



