Prof. M. Schultze on Hyalonema. 159 



Dr. Gray, printed at p. 397, has maintained, in accordance 

 with my view, that Hyalonema is not a coral, but a sponge. As 

 I think that he has not defended his conviction of the mutual re- 

 lation of the '' Glass Rope " and the sponge adhering to its lower 

 extremity with such striking arguments as, in my opinion, have 

 been put forward in the preceding article, I do not regard the 

 publication of my remarks as superfluous. Dr. Bowerbank 

 promises a com])lete monograph upon Hyalonema, in which he 

 intends to prove that the polype-coat of the " Glass Rope '' is 

 not a polype, but also a portion of the sponge ("a cloacal 

 system ^^). Here, therefore, we have a third view as to the 

 nature of Hyalonema^ according to which the concurrence of a 

 parasite is entirely excluded. • 



Dr. Bowerbank supports his opinion upon the fact that the 

 same cruciform spicules which are characteristic of the sponge 

 of Hyalonema occur also in the supposed polype-coat. I admit 

 that this circumstance is very likely to lead one to agree with 

 Dr. Bowerbank in opinion. I also admit that, after my first 

 microscopic examination of the specimens at Leyden, I favoured 

 the same opinion that Dr. Bowerbank expresses (see 'Comptes 

 Rendus/ 23rd April, 1860, p. 792). But the careful examina- 

 tion of the cortical layer in question proves incontrovertibly that 

 it consists of polypes and is no part of the sponge. When the 

 bark of well-preserved specimens is softened in water, or espe- 

 cially in dilute solution of potash, not only do the tentacles of 

 the polypes make their appearance in their characteristic form 

 (see taf. v. fig. 4 of my monograph), but the higher powers of 

 the microscope even show that the tentacles and many other 

 parts of the polypes are beset with unmistakeable urticating 

 organs. These are in part of comparatively large size, and present 

 an internal rolled thread like the fresh urticating organs of the 

 polypes and medusae, leaving not the smallest doubt that we 

 have to do here with true Polypes. All this I have already 

 described in detail and illustrated with figures in my monograph 

 (1860) above quoted. Dr. Bowerbank has made no mention of 

 these circumstances ; and also in his memoirs published in the 

 'Philosophical Transactions' (vol. clii. part 2, 1862, pp. 747 & 

 1087, plate 31. figs 3-6), in which he figures the siliceous spi- 

 cules of Hyalonema, there is no intimation that several years 

 previously I had already described these spicules, in my opinion, 

 much more perfectly. 



After the preceding statements, the circumstance that scattered 

 siliceous spicules are imbedded in the skin of the polype can no 

 longer furnish evidence that in these polypes we have only a 

 " cloacal system " of the sponge, as Dr. Bowerbank thinks ; for 

 we know that Palythoa and other Zoanthidce take up foreign 



