J. G. WALLER OX AN UNDESCRIBED BRITISH SPONGE. ZOO 



extreme difficulty in accurately delineating them. Few of these 

 figures, though beautifully executed, are sufficiently defined in the 

 "British SjDongiadre," and in many instances do not seem to be 

 quite understood. But the late H. J. Carter's representations 

 are very different : nothing can be more precise and accurate ; 

 especially when we consider how" very easy it is to make a mistake 

 by omitting important, but obscure details. The same care is also 

 to be found in the figures given in the CJudlenger reports. It 

 was Mr. Carter, however, who first described these spicules in all 

 their details, accompanied by renderings which commend them- 

 selves by their truth. I shall here, in presenting before you the 

 forms found in this sponge, compare them with what are seen in 

 genera or species with which I think this must be associated. 



And one cannot trust to any description but what is general, 

 and illustrations are inevitable. But before one does this it may 

 be well to quote some observations on '• flesh spicules " as given in 

 a paper by Professor K. A. Zittel on fossil Hexactinellidse, in the 

 Annals and Magazine of Natural History, 4th series, vol. xx., 

 p. 272. He says, " If we take our stand on the ground of the 

 transmutation theory, we certainly have before us in the flesh 

 spicules those parts of the sponges which change most readily by 

 adaptation, and therefore most easily throw off" the original type." 

 Every one who has had any experience must assent to this ; and, 

 in now placing before you some examples, it will be easy to affirm 

 the wisdom of these remarks, and how utterly useless it would be 

 to use them as distinctive of species except in general terms. The 

 changes which take place in vegetable forms from very slight 

 causes, as displayed in our gardens, teach us that nature rejects 

 the restriction of species. It is, however, a scientific necessity to 

 mark changes observed in cognate organisms by an addition to the 

 generic term, but this should be done with judgment and with as 

 much simplicity as possible. 



To return to those details which seem inevitably to point out 

 the group under which this sponge must be arranged : they consist 

 primarily of those fasciculi which distinguish the genus Raphio- 

 desma, as well as those anchorate spicules of the character 

 belonging to it, and the tendency to form rosettes, though incom- 

 plete, at least in the specimen under consideration. Also the 

 associated forms, tricurvate, and those I arrange under bihamate, 

 though doubtful of the accuracy of the term as terminal hooks are 



