REPORT ON THE MONAXONIDA. xiii 



delicate tissues when necessary, and to communicate to tliem a certain amount of tension 

 when it is required," while " the office of the second class is that of assisting in the 

 retention and protection of the sarcode on the interstitial and other membranous 

 structures." Leaving aside the question as to what an interstitial membranous 

 structure may be, we may point out in passing that these statements are based upon 

 unproved theory. 



As to the forms assumed by many of the spicules, Bowerbank's work is also 

 unsatisfactory. No one could well go wrong with regard to the larger " essential 

 skeleton " spicules, and we consequently find these correctly figured in the plates, but the 

 terminology employed to describe them is most unfortunate ; who, for example, could 

 bring himself to make use of the term " Fusiformi-attenuato-cylindrical," ^ or " Exflected 

 elongo-equiangulated triradiate,"^ in describing the spicules of a sponge'? 



To discover the true form of many of the more minute spicules (" auxiliary " spicules) 

 is, it must be confessed, a difficult task, still it is hard to see how such a careful 

 observer as Dr. Bowerbank can have been so far misled as he was in this respect. The 

 imperfections of his descriptions and figures show themselves in the very important 

 grouj) of so-called " anchorate " s^^icules [ = cliela3, nobis). Quite correctly he distinguishes 

 between two main divisions of these, the equal ended and the unequal ended, but as to 

 the true shape of either of these he seems to have had very little idea. He subdivides 

 both categories into "bidentate," "tridentate," and "palmate." The tridentate and 

 palmate forms, as he himself indicates, run into one another, while a mere tyro, by the 

 examination of Dr. Bowerbank's figures and comparison of these with actual specimens, 

 may satisfy himself in a very short time that the " bidentate " form is neither more nor 

 less than a side view of either of the other two. Yet again and again do we find sponges 

 described by Dr. Bowerbank as possessing two kinds of " anchorates," the two views 

 being carefully figured as distinct spicules.'' On pi. xlvi., vol. iii. of the Monograph of 

 British Sponges, for example, fig. 12 is obviously the side view, and fig. 13 the front 

 (or back?) view of the same spicule, but we find the following descriptions:— "Fig. 12. 

 — A bidentate, inequi-anchorate, retentive spiculum, from the dermal membrane. x 530 

 linear. Fig. 13. — A dentato-palmate, inequi-anchorate, retentive spiculum, from the 

 interstitial membranes, x 530 linear. This form of spiculum was not observed in the 

 specimen of the sponge first examined. In the specimen figured they are about equal 

 in number to the bidentate spicula." Moreover, the figures of the spicules are rarely 

 complete, the " anterior palm," owing to its great transparency difficult to make out, 

 being almost invariably omitted. 



It is in our opinion of the greatest importance that these errors should be corrected, 



' Op. cit.., vol. i. p. 231. 2 Op_ „■(_, vol. i. p. 233. 



3 The shape of the " bidentate equianchorate " spicule will be found elaborately, though somewhat unintelligibly, 

 described on p. 46, vol. i., Mon. Brit. Spong. 



