round tin' CtUum of the Spongc-ceV. f 



in cliuitcrs on branches of the delicate little seaweed culled 

 Ca/lithamnion roaeunij ■Nvhieh tringes the overlKUi<;ing edges 

 anil under surtaees of the roeks here, about midway between 

 high- and low-water mark, where it is left uncovered by the 

 water for some hours twice a day. 



Thinking, therefore, from its hardiness, that it might serve 

 to eontirm Trof. James-Clark's observations on Lcucosolcnia 

 botrt/oi'des (L o.), I, about six weeks since, brought home some 

 branches of the CaUithamnion bearing specimens of Grantia 

 compre^so, which were put into salt water on the snot ; and 

 the day after, as these sponges were still living, X tore up 

 some jiieees and placed them under the microscojje, with |-ot- 

 an-inch compound power for observation, Avhen, mueh to my 

 ffratiHcation, 1 witnessed exactly what Prof. James-Clark had 

 dcf^cribed, as may be seen by reference to the four groups of 

 figures (18-16 in PI. I.) which were then made from them. 

 I also saw immediately that the " ear-like ])oints or spines " 

 on the monociliated sponge-cell of Sj>om/ ilia ^ which maybe 

 found full}' described and figured in the 'Annals' (Jan. 1859, 

 vol. iii. p. 14 cNcc, pi. 1. ligs. 12, 13, 14) were, as Prof. 

 James-Clark had suspected (footnote, p. 21, loc.cit.), "the 

 right and left profiles of a membranous cylinch-ical collar." 



Feeling satisfied that Prof. James-Clark was right in his 

 interpretation of this form of sponge-cell, and having, by ex- 

 periments on Sjjonffi'lla, as may be seen in my figures (/. c), 

 showed that, when immersed in a solution of indigo, the 

 sponge-cells with " ear-like points " became more or less filled 

 with it, I, of course, thought that the sponge-cells of Grantia 

 compressa might do the same, when it would become satisfac- 

 torily evident that the same kind of ciliated sponge-cell existed 

 in both the siliceous and calcareous sponges. 



Accordingly, about a fortnight since, I took a branch of 

 CaUithamnion rosevm on which there was a cluster of Grantia 

 covij^ressa^ and, having placed it, as before, in sea-water on the 

 spot, brought it home, rubbed down a little indigo, also in 

 sea-water, and put the cluster into it. 



After about an hour, all the specimens of Grantia compressa 

 became of. a dark-blue colour ; and on cutting out a minute 

 portion of one and tearing it to pieces, still in sea-water, the 

 fragments were thus placed under the microscope, on a glass 

 slide under a glass cover, when, equally to my gratification, I 

 found the collared monociliated cells more or less filled with 

 indigo, and in active vitality (PI. II. fig. 30). 



Kext the cluster was placed in clean sea-water, and a stream 

 of indigo was observed to be gradually flowing from the vent 

 of each specimen respectively. 



