230 Mr. A. Hancock on the Excavating Sponges, 



volume (p. 216) of liis recently published 'Monograph of the 

 British Spongiadse/ that I have divided Dr. Johnston^s Halt- 

 chondria celata into twelve species. It does not appear that 

 Dr. Johnston ever saw any one of the species described by me ; 

 there is certainly nothing in his description to show that he had 

 examined more than one form of Cliona'^. Neither do I see any 

 reason for believing that Dr. Bowerbank himself has enjoyed 

 any greater advantage ; for if he had had in his possession spe- 

 cimens of my species, he assuredly would never have written 

 that "nearly all these proposed new species have the same habit 

 and the same forms of spicula, with only such an amount of 

 variation in size and form as may readily be found in a single 

 field of view beneath the microscope in any well-known specimen 

 of Halichondria celata of Johnston, when mounted in Canada 

 balsam"t' " Now I have numerous slides, so mounted, of Cliona 

 celata, Grant, which species is undoubtedly the same as John- 

 stones second variety under that specific denomination, and I 

 have never found on any of them more than one form of spicu- 

 lum, or any of the forms that characterize Cliona Northumhrica, 

 C. gracilis, C. Hoivsei, C. Alderi, C. corallinoides, C. lobata, or 

 C. vastijica; neither have I, in any of these species, found the 

 exact form of spiculum that distinguishes C. celata. In fact 

 the habit of the sponge and the characters of the spicula are so 

 well pronounced that, with the exception of one, which I admit 

 to be critical, few naturalists, after a careful examination of the 

 species I have described, will doubt their distinctness. 



And here it may be observed that the study of C. celata alone 

 is not sufficient for the full comprehension of the questions con- 

 nected with the excavating Sponges. This species is not by any 

 means typical of the group : it has but one form of spiculum, 

 while by far the greater number have two or three kinds, and 

 the sponge itself does not assume in a decided manner that 

 lobed structure which is sp dominant among the species. All 

 the British forms should be carefully examined ; and the foreign, , 

 which are very abundant, should be investigated with equal 

 assiduity. When this is done there will be little difference of 

 opinion on most questions connected with the subject. 



When I drew up the descriptions of the species, I had not 



* This, however, does not appear to have been Dr. Johnston's own 

 opinion. In a letter I had the pleasure of receiving from that excellent 

 naturalist shortly after the publication of my pa])er on Cliona, speaking 

 on this subject he says, " I have no doubt my C celata embraces several 

 species." But this was a hasty utterance, written on the spur of the mo- 

 ment, and probably meant nothing more than an expression of his convic- 

 tion that there are more than one species of British Cliona. 



t Monograph of the British Spongiadae, vol. ii. p. 216. 



