Royal Society. 291 



cumstances we have substituted the latter name for the one 

 adopted in the paper. 



The author also states that the animal described by Kolliker 

 under the name o{ Actinophrys Sol, is the ^. Eichhornii, Khrb., 

 but adds, that specimens of that species, which came under his 

 notice after the printing of his paper had commenced, agreed 

 exactly, in regard to the contractile vesicle, with those which 

 formed the subject of his previous investigations. He did not 

 observe it in the act of feeding. 



He also states that Arcella vulgaris possesses as many as ten 

 contractile vesicles, and that he was in error in ascribing only 

 two of those organs to that Rhizopod. — Translator.] 



EXPLANATION OF PLATE YIIL 



The letter o indicates tlie contractile vesicle throughout all the figures. 

 Fig. \. Actinophrys Sol, in its ordinary sun-like form. 

 Fig. 2. A. Sol, in the act of division or conjugation, with two contractile 



vesicles. 

 Fig. 3. An Actinophrys in the act of feeding. A Chlamidomonas and an 



Astasia have just been enclosed by the slimy substance. 

 Fig. 4. An Actinophrys in the act of pushing out the slimy substance 



(a and b). 

 Figs. 5 & 6. Peculiar and unusual forms of ^. Sol. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL. SOCIETY. 



January 18, 1855. — Sir Benjamin Brodie, Bart., in the Chair. 



" On the Dots upon the Valves of the Diatomaceae." By J. W. 

 GrifSth, M.D., F.L.S. 



In a former paper, it was stated that the markings or dots 

 upon the valves of the Diatomaceae, are the optical expressions 

 of depressions existing upon the valves. 



All those authors who have paid special attention to the Diato- 

 maccce, have considered the markings to denote cells ; among these 

 we find Ehrenberg*, Kiitzingf, KalfsJ, Smith§, and Quekett||. 



The evidence I adduced in regard to the more coarsely marked 

 Diatomacese, as IstJimia, &c., being furnished with depressions and 

 not cells, is, I believe, satisfactory and conclusive ; and this view 

 has been admitted in a paper since read before the Royal Society 5[. 



A different view has been taken of the nature of the finer mark- 

 ings, as those upon some species of Gyrosigma, by the author of the 



* Die Infusionsthierchen. f Die Bacillarien, aud Spec. Algarum. 



X Annals of Nat. Histon-, 1843. § British Diatomaceje. 



II Histological Catalogue of the College of Surgeons ; and Lectures delivered 

 before the College of Surgeons. 



^ Proceedings of the Roval Society, June 15, 1854. 



19* 



