14 Mr. H. J. Carter on Spongilla. 



and the spore-cells arising from a number of the cortical cells 

 becoming impregnated and projecting into the interior^ as in 

 Volvox, might thus altogether become surrounded by the sili- 

 ceous cortical structure common to the sporangia or seed-like 

 bodies of Spongilla, and so form the sporangia. But this should 

 have no other influence than that of exciting a desire to pursue 

 still further the history of this hybrid organism, which, though 

 as it were at the angle from which the two great organic king- 

 doms diverge, and therefore assumed to be extremely simple in 

 its organization and oeconomy, is much more complicated in 

 both than the common theorist would be inclined to conceive. 

 It might, however, be observed, that the spherical sac is only 

 l-540th, while the adult Volvox is l-33rd of an inch in diameter ; 

 but on a reference to M.'N. Lieberkuhn's description of the 

 "swarm-spore" of Spongilla^, it will be observed that this 

 (which appears to me to be a development from the spherical sac, 

 and is also similarly coated with a layer of monociliated cells) 

 can be seen with "the naked eye, being l-35th [55th] of an 

 inch in length." 



Another point to which I have lately directed my attention 

 again is the ciliated sponge-cells; for, seeing that M. N. Lieber- 

 kuhn had discovered some which he considered " spermatozoa- 

 like bodies f/^ and that they were not like those which I thought 

 might be suchj, I determined to test the monociliated body, 

 which appeared to me most like a spermatozoon, by placing 

 some indigo in the water with a small portion of living Sjwn- 

 gilla selected for the purpose, and then breaking it up for view 

 under the microscope, when, if these bodies had taken in any 

 portion of the colouring matter, I should conclude that they 

 were not spermatozoids. 



Now there are monociliated cells of different sizes in Spon- 

 gilla, some of which are now known to belong to the cortical 

 layer of the spherical sacs, and which I have already shown to 

 take in colouring matter; but there is one in particular, which 

 has two spines or ear-like points projecting backwards, one on each 

 side of the root of the cilium (PI. I. fig. 12), and this was the kind 

 which I first discovered and described ; but, confounding it with 

 cells not possessing these spines, because I then thought the spines 

 might be accidental prolongations of the sarcode, I did not give 

 it this character; and the smooth cells being largest, the size I 

 gave for them of course exceeded that presented by the cell with 

 spines, that is, being smallest where these parts are smallest, 

 which is in S. cinerea. In S. plumosa (fig. 12) it is about the 



* Annals, vol. xvii. p. 407, 1856. f Annals, vol. xvii. p. 412, 1866. 

 X Annals, vol. xiv. p. 334, 1854, 



