Royal Society. 291 



cumstances we have substituted the latter name for the oijie 

 adopted in the paper. 



The author also states that the animal described by Kolliker 

 under the name of Actinophrys Sol, is the A. Eichhornii, Ehrb., 

 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. ^"j 



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 VHL 



The letter o indicates the 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 substanc;^ 



[a and b). 

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



T 



;^. PROCEEDINGS OF LEARNED SOCIETIES. 



tSbiay ROYAL SOCIETY. ?^ 



fivr/;; ... . O^- 



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



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

 Griffith, M.D., F.L.S. ^I 



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

 upon the valves of the Diatomacese, are the optical expressions 

 of depressions existing upon the valves. 



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

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

 we find Ehrenberg*, Kiitzingf, RalfsJ, Smith§, and Queketty. 



The evidence I adduced in regard to the more coarsely marked 

 Diatomacese, as Isthmia, &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^. 



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

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



'•' Die Infusionsthierchen. f Die Bacillarien, aiid Spec. Algarura. 



X Annals of Nat. Histoiy, 1843. § British Diatomaceae. 



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

 before the College of Sui'geons. j^ 



*[f Proceedings of the Royal Society, June 15, 1854. 



19* 



