484 Transactions of the Society. 



change has been brought about, but it is important to notice it, 

 for the appearances are sufficiently well marked to be very decep- 

 tive ; and it is the more difficult to explain -when it is known that 

 a specimen, also from Montagu, still exhibits quite clearly and well 

 the spiculation of C. doliolum, while yet another which has not been 

 in spirit for thirty-five years has the spicules broken down beyond 

 recognition. 



Too much trust must not, therefore, be placed on the Micro- 

 scope as a means of determining the specific relationship of some of 

 the forms described by naturalists who did not themselves make 

 use of this weapon of research ; unless the greatest care is per- 

 sistently taken in the preservation of specimens, the dermal and 

 hypodermal layers with the concretions therein developed may 

 become broken down or altered. Indeed, at present, no time 

 could be more usefully spent by a microscopist than that which 

 should be devoted to the careful study and description of even the 

 spicules of the British species of Holothurians ; for the worker of 

 to-day the descriptions of Edward Forbes are found to be in- 

 complete and unsatisfactory, in consequence of the total lack of 

 information concerning these important structui'es. 



