322 Dr. Dickie's Notes 0/ Diatomacese 



where, especially towards their outer extremities. It is the 

 Y^jth of an inch in diameter. 



My specimen consists of at least three layers inclosing two 

 inner cavities, which contain a green endochrome. In this it 

 resembles many other allied forms. From what has appeared to 

 be a single disc of Arachnoidiscus Japonicus, I have separated as 

 many as six siliceous layers. 



This separation into laminae, marking the existence of so many 

 individual frustules, reminds us of Meloseira and its allies ; — a 

 resemblance that becomes the more striking, when we remember 

 that as in Meloseira, the first frustules oi Arachnoidiscus, Cocconeis 

 and many others are attached, as parasites, to some other body. 

 In the analytical table of the Bacillarice originally given by 

 Ehrenberg he includes many of these objects ; classing Cocconeis, 

 Actinocyclus, and what he calls Bacillaria, together in his group 

 of Naviculacece, and characterizing them as " free," in contradi- 

 stinction to his "fixed" forms, in which latter he includes Isthmia 

 and other genera. It appears evident, however, that Cocconeis 

 and Arachnoidiscus are as " fixed " when found . in situ as any of 

 the Diatomacea, and probably many of these other allied genera 

 will eventually be found to exhibit the same feature when better 

 known. I have elsewhere* endeavoured to show the close rela- 

 tionship which exists between these discs and the already recog- 

 nized Diatomacece, and I cannot but think that by the time my 

 enthusiastic friend Mr. Ralfs resumes his valuable labours upon 

 the British species of this interesting group, he will find it ne- 

 cessary to include in his classification a large portion of our native 

 species of what are commonly called " Siliceous Infusoria." 



I would propose for the above species of Campylodiscus the 

 name of C horologium. . , 



Manchester, March 23, 1848. 



XXXIII. — Notes 0/ Diatomacese /oMwt/ in the stomachs of certain 

 Mollusca. By George Dickie, M.D., Lecturer on Botany in 

 the University and King^s College of Aberdeen f. 



Professor E. Forbes has remarked that the stomachs of fishes 

 are often zoological treasuries. The Haddock is a great concho- 

 logist ; the Cod is more devoted to the Echinodermata, having a 

 great taste for that tribe. 



Certain Mollusca are equally indefatigable collectors of Dia- 

 tomacea ; they have been found in the stomachs of the Oyster, 



* Memoirs of the Manchester Literary and Philosophical Society, vol. viii. 

 p. 48 et seq. 



t Read before the Botanical Society of Edinburgh, March 9, 1848. - 



