Dublin Natural History Society, 431 



hers of the Society, and they had detected in them many forms of 

 minute animals which were new to English microscopists. 



Another communication was also read by the Secretary from C. G, 

 White, Esq. of Poplar. It will be recollected that in October 1840. 

 Mr. White exhibited to the Society some beautiful specimens of sup- 

 posed minute fungi, which he had found in tolerable abundance on 

 gravel stones in the neighbourhood of Old Ford, Middlesex ; they 

 corresponded in some measure with the description of Craterium pyri- 

 forme as given by Hooker and other botanists. Mr. White, having 

 paid considerable attention to ascertain their true nature, has at last 

 found them not to be of a fungoid nature, but the ova of a species of 

 Acarus, with a body of a red colour and six legs ; specimens of the 

 insects, both in the e^^ and after their escape, were exhibited to the 

 meeting. 



DUBLIN NATURAL HISTORY SOCIEtV. 



The usual monthly meeting of the Members was held on Wed- 

 nesday the 1st instant, J. W. Warren, Esq., in the Chair. 



At this meeting a paper communicated by Arthur Hill Hassall, Esq., 

 entitled, "A Sketch of the Freshwater Confervae," was read by the 

 Secretary. 



On the subject of the growth of the Confervae, Mr. Hassall makes 

 the following observations : — 



** The rapidity of growth of most species of Confervae has been a 

 subject of surprise to many observers of nature, and the explanation 

 which I am about to offer of the causes of this very rapid growth has 

 not, that I am aware of, been before noticed. Most, if not all, the 

 Confervas appear to me to increase in two ways; first, by the con- 

 tinued growth of the free extremities of the different filaments : this 

 method is obvious and need not be insisted on. Secondly, by the re- 

 peated growth and subdivision of each cell entering into the forma- 

 tion of the filaments. I long suspected the existence of this mode of 

 development, but was first convinced of its reality by an examination 

 of those species of the genus Conjugata of Vaucher distinguished by 

 the presence of spiral tubes winding round the interior of the cells, 

 and especially of the one named Conjugata princeps. If the filaments 

 of this species be carefully examined and contrasted together, it will 

 be seen that in some the length of the cells only just exceeds their 

 diameter, and that each cell contains three spiral tubes, which toge- 

 ther perform from seven to eight turns in each, the coils almost touch- 

 ing each other ; that in others the length of the cells is more than 

 three times the diameter, but that still each cell contains only the 

 same number of spiral turns, viz. seven or eight, which now, instead 

 of being nearly in apposition, are widely separated, thus plainly pro- 

 ving the elongated cells to be derived from the growth of the short- 

 est ones ; and again it will be noticed in others that the cells have 

 returned to their original length, but that each now contains only 

 three or four spiral turns, thus manifestly proving the division of the 

 elongated cell, and completing the chain of evidence which establishes 

 to demonstration the existence of the mode of growth to which I 



