242 Mr. W. J. Sollas on the 



even by Lamarck himself, in close connexion with Alcyonium, 

 and was regarded as a member of the same family. Lamarck's 

 description of his genus is as follows : — " Polyparium liberum 

 carnosum tuberiforme intus cavum et vacuum, in sicco du- 

 rum ; externa superficie undique porosa. Foramina poris 

 majora, in area unica orbiculari et laterali acervata." On 

 page 334 (loc. cit.) he concludes his observations with the 

 remark, " .... la forme d'une geode close et la facette 

 orbiculaire, et en crible que l'on observe sur les Geodies, 

 constituent leur caractere ge*nerique." A single species, 

 Geodia gibberosa, Lamk., is given as the type. 



In 1828 Fleming * took from the Alcyonia another Geodine 

 genus, and gave it the name of Cydonium. His definition is 

 thus given : — " A coriaceous skin, internally carneous, with 

 numerous straight-ridged spicula perpendicular to the surface ; 

 polypi with a central opening, and an orifice at the base of 

 each of the eight pinnated tentacles." His type is given as 

 Cydonium Miilleri {A. cydonium. Mull. Zool. Dan. t. Si. 

 f. 3, 4, 5, a, and Jameson, Wern. Mem. i. p. 563). In his 

 observations he states that the skin consists of animal matter 

 cementing innumerable siliceous grains, and that the spicules, 

 which are collected in bundles and radiate from the centre, 

 become in many cases trifid or tricuspidate immediately under 

 the skin. 



Nothing could be clearer from this description than the fact 

 that Fleming had before him a genus of genuine Geodine 

 sponge. There can be no doubt about this ; but if there were it 

 would be immediately dispelled by a reference to the figure 

 given by Bowerbank f of Fleming's original type, which is a 

 typical Geodia zetlandica, Johnston. 



It is remarkable that Fleming should have attached to this 

 sponge the characters of an Alcyonian polype ; nor can it be 

 explained by easily-made references to the vigorous imagina- 

 tions of the early naturalists ; it seems more likely that the 

 explanation may be of the following nature. The spicular 

 characters of Cydonium Fleming had observed for himself; the 

 Alcyonian characters he could not have observed, because they 

 did not exist; but he identified his sponge with Alcyonium 

 cydonium in Muller's Zool. Dan. {loc. cit.), which, from 

 Miiller's clear and apparently faithful drawings, is evidently a 

 true Alcyonium. Fleming next proceeded to add the charac- 

 ters of Muller's specimen to those of his own, and thus pro- 

 duced the curious hybrid we find in Cydonium Miilleri. Such 

 cases of mistaken identification are not, I believe, altogether 



* British Animals, p. 516. 



t Bowerbank, ' British Sponges,' iii. 



