Mr. A. H. Hassall on the genus Ecliinocoriuni. 117 



culiar effect in polarizing light. There is only one circumstance 

 more worthy of mention, and which is very common but very inju- 

 rious : it is the placing too much of an object on a slide at once ; this 

 often renders a beautiful object of little value. I need hardly say 

 that it is better, if possible, to preserve most specimens under thin 

 glass, so that at any future time they can be examined by the high 

 powers of the microscope, if necessary. 

 9 St. John's Square, July 21, 1843. 



XYIII. — Obsei'vations on Two of Professor Edward Forbes' s 

 " Retrospective Comments" By Arthur Hill Hassall, Esq. 



Professor Edward Forbes, in a paper entitled " Retrospective 

 Comments," a portion of which is inserted in the ^ Annals^ for 

 July 1843, makes some remarks on the genus Echinocorium, and 

 on the Phosphorescence of Zoophytes, on both of which I wish to 

 oflFer a few observations. ]\Ir. Forbes appears to reject my genus 

 Echinocorium on the twofold ground, that the zoophyte which I 

 regard as its animal is sometimes met vaih unconnected with the 

 polypidom, and that in those cases in which the two are asso- 

 ciated, no organic bond of imion exists between them. With 

 regard to the lii'st point, the result of my experience is, that the 

 polj^e is never met with but in connexion vni\x the polypidom, 

 and that its distribution is always limited to that portion of the 

 shell covered by it ; and I may remark, that I have very frequently 

 obtained the liA"ing zoophyte. With reference to the absence of 

 structural connexion, Mr. Forbes observes, " Had !Mr. Hassall 

 looked a little closer to his specimens, he would have found that 

 there is no organic connexion between the parasite and its base, 

 and that each Coryne is an independent animal, capable of de- 

 tachment without injmy." I beg to assm-e ]Mr. Forbes that I 

 did look very closely to my specimens, and that the issue of my 

 examination of them was a conviction of the reality of a bond of 

 imion, — a conviction arrived at by the observation of the follomng 

 particulars, \dz. that marked depressions existed in the polypidom 

 for the reception of the bases of the polj^pi; that the whole 

 structure of the pohiiidom itself was porous and incorporated 

 mth gelatinous material ; and lastly, that it was also encrusted 

 by a membrane derived from the pol\"[3i themselves, and which 

 likewise covered the muricated processes. These facts, if not con- 

 clusive, are yet I hope sufficient to exonerate me from the charge 

 of having " too hastily constituted the genus Echinocorium," and 

 show that I did exercise a common degi'ee of caution. Besides, 

 supposing Mr. Forbes to be correct as to the independence of the 

 polype regarded by me as the true zooph)i;e of Alcyonidium echi- 

 natum, which I am far from being satisfied that he is, still this 



