456 Mr. H. J. Carter on the 



LVI. — Further distances of the Sponge- Spicule in its Mother 

 Cell. By H. J. Carter, F.R.S. &c. 



[Plate XXI. figs. 26 & 27.] 



Since my description and figures of the mother cell of the 

 sponge-spicule were published (' Annals/ 1874, vol. xiv. 

 p. 100, pL x.), I have met with two more examples where the 

 cells respectively enclosed a single tricurvate (flesh-spicule) 

 so nearly approaching in length and form (in one instance 

 especially) to a skeleton-spicule, that I have given representa- 

 tions of them in Plate XXI. figs. 26 & 27, to show also how 

 a long, linear spicule may be thus enclosed throughout in an 

 equally long, bolster-shaped or tubular, nucleated sponge-cell. 



Figure 26 comes from a variety of Esperia a>gagropila y 

 Carter ; and although much thinner than the skeleton-spicule of 

 this species, it is so slightly undulous and so much longer than 

 the latter, that it might be easily mistaken for a second form 

 of skeleton-spicule, which is contrary to one of the characters 

 that I have assigned to the Esperiadse, viz. that they only 

 possess one form of skeleton-spicule. Finding it, however, in 

 a cell (fig. 26, Z>), and seeing it more tricurvate in form in the 

 ovum of the parent (fig. 25), there was no difficulty in con- 

 cluding that it was the tricurvate of this variety of Esperia 

 cegagropila. As it appears in the adult it is linear, very thin, 

 smooth, slightly undulous (fig. 26, a), and longer than the 

 skeleton-spicule both in the parent and in the ovum which 

 has nearly arrived at the embryonal degree of development 

 (fig. 25, e) ; so that we may fairly assume that this, which is the 

 chief peculiarity of the variety, is constant. In measurement 

 it is more than twice the length of the tricurvate in the typi- 

 cal species, which, on the other hand, gains in stoutness 

 what it loses in length, the former being 90-6000ths inch long. 

 Growing in small patches scantily on the rocks (at Budleigh- 

 Salterton) towards low-water mark, it (with the exception of 

 possessing a much smaller bihamate) agrees with the typical 

 species, viz. Esperia cegagropila, in the form and size of its 

 single inequianchorates as well as in their rosette-forms, together 

 with all the other characteristics of the latter. 



Figure 27, on the other hand, comes from a distinct species of 

 MlCROClONA, Bk., in which the small, abruptly subangular form 

 of the tricurvate in the centre of the spicule contrasts strongly 

 with its greatly extended and almost straight arms. Ending in 

 spined extremities, however, causes it to differ from all the 

 species described by Dr. Bowerbank, although that called "M. 

 armata" (B. S. vol. ii. p. 129) seems to come so near to it 

 that I cannot help thinking that, if it had been more accu- 



