74 RIOHAED EVANS. 



(a) The first group of spicules consist of diactinal monaxons 

 or ampliioxea, wliicli are usually curved^ tliougli straight 

 specimens are occasionally seen (PL 1, fig. 3, a — e). 



(6) The second group also consists of curved aniphioxea, 

 but for reasons which will be stated further on they are sepa- 

 rated from the first group (PL 1, fig. 3,/). 



(c) The third group consists of amphidiscs, which may be 

 present in a fully developed or in an immature form (PL 1, 

 figs. 3^ g — m, 4, a — c). 



(a) The amphioxea belonging to the first group taper 

 gradually to a sharp point. They are never provided with a 

 swelling at the middle point of the shaft, and scarcely ever 

 are they malformed or modified in any way. In both respects, 

 therefore, they differ most strikingly from the spicules of 

 Spongilla moorei, a description of which was published in 

 this journal a year and a half ago. They appear to be in- 

 variably covered with small spines, 



(&) The amphioxea belonging to the second group are 

 invariably curved and covered with small spines. In fact, 

 they present the same characters as the spicules of the 

 first group, but differ from them in being only half as long 

 and less than half as thick. They are not found in the 

 general tissues of the sponge or in its membranes, but are 

 grouped together round small bodies^ which are embedded in 



' The bodies above meiilioiied seem to possess a definite outline, and to 

 lie in cavities of tlieir own, much in tlie same way as the gemmules (Pi. 4, 

 fig. 17). I have no conception what these bodies are, but several solutions 

 have suggested themselves. Unfortunately T have been unable to find them 

 in thin sections, and consequently cannot speak of their internal structure. 



The first suggestion, witli regard to their nature, to present itself was that 

 they were a second kind of gemmule. Tiie arrangement of the spicules round 

 them reminds us of tiiat of the spicules round the gemmules of Spongilla 

 lacustris, and is, so far, in favour of the supposition that these bodies are 

 some kind of gemmules. But apart from the fiict that Ephydatia blem- 

 bingia possesses anotlier kind of gemmule, these structures are much more 

 transparent than ordinary gemmules are at any stage in their development or 

 when they are mat\ire. if they were gemmules their basket-like shape could 

 be easily explained as the result of contraction under the action of preserving 

 reao-ents, owing to the cuticular coat being extremely thin. Apart from the 



