Mr. A. H. Hassall on the genus Echinocorium. 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. 



XVIII. — Observations 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 

 offer a few observations. Mr. Forbes appears to reject my genus 

 Echinocorium on the twofold ground, that the zoophyte which I 

 regard as its animal is sometimes met with unconnected witli the 

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

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

 regard to the first point, the result of my experience is, that the 

 polype is never met with but in connexion with 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 living 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 injury .^^ I beg to assure 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 

 union, — a conviction arrived at by the observation of the following 

 particulars, viz. that marked depressions existed in the polypidom 

 for the reception of the bases of the polypi ; that the whole 

 structure of the polypidom itself was porous and incorporated 

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

 by a membrane derived from the polypi 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 degree of caution. Besides, 

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

 polype regarded by me as the true zoophyte of Alcj/onidium echi- 

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



