DUBLIN MICROSCOPICAL CLUB. 305 



List of Diatomaceous species found in a Sample of Earth from 

 Qermany, said to be employed in the manufacture of Dynamite. — 

 Dr. Barker showed, ou the part of Mr. A. M. Vereker, a sample 

 of Diatomaceous earth from some locality in Germany ; the 

 material is said to be employed in the manufacture of dynamite. 

 Mr. O'Meara identified the species and furnished the following 

 list : 



Amphora ovalis, A. minutissima, Cocconema lanceolatum, C 

 parvum, Cymbella cuspidata, G. maculata, CycloteUa operculata, 

 JEpithemia alpestris, E. argus, E. Syndemanii, E. longicornis, E. 

 sorex, E. turgida, E. zebra, Gomphonema intricatum, G. dicho- 

 tomum, Navicula Anglica, N. lacustris, iV. limosa, N. limosa, var. 

 gihberula, N. affinis, JSf. dubia, Orthosira arenaria, Synedra 

 amphirhyncus, 8. longissima, 8. ulna. 



Microsporon mentagrophytes, exhibited. — Dr. W. M. A. Wright 

 showed filaments of the hair-parasite Microsporon mentagrophytes, 

 disputed by some as beiug only an abnormal or disorganized con- 

 dition of the hair. 



On the antheridia in Polysiphonia nigrescens. — Professor E. 

 Perceval Wright exhibited the quite recently gathered anthe- 

 ridia of Eolgsiphonia nigrescens. So far as he knew, the descrip- 

 tions of the antheridia in this genus left much to be desired, and 

 the figures of them in most works on descriptive algology gave 

 only the appearances as seen in dried specimens. In the speci- 

 mens of the above species gathered early in February, the anther- 

 idia appeared to arise in an outgrowth of what, in contrast to 

 the '■ siphonal cells," might be called the "cortical cells," of the 

 extreme sides of the twigs, the antheridial cell being the enlarged 

 basal cell of a trichome-like prolongation which started from 

 one of the cortical cells, which itself projected at an angle from 

 the main twig ; above the enlarged basal cell there were to be 

 found, when the structure was complete, from five to seven other 

 cells gradually tapering to a hair-like point ; these were most 

 easily broken off". Surrounding the antheridial ceil and its hair- 

 like prolongation were a series of long dichotomously divided 

 filaments, which, when the entire mass was observed in a growing 

 state, seemed to act as conducting or collecting hairs for the an- 

 therozoids, which made their escape through the ruptured cell- 

 wall of the antheridium. The antherozoids themselves, when 

 freshly escaped, seem to be provided with no very definite cell- 

 wall, neither did they seem to be the products of special mother- 

 cells, but rather specialised portions of the protoplasmic contents 

 of the antheridial cell. 



On a Cosmarium-form seemingly the same as Jacobsen^s so-called 

 var. of Cosm. Brebissonii. — Mr. Archer showed examples of a small 

 lorm of Cosmarium from Co. Carlow. This comes near to the 

 form figured by Jacobsen in ' Copenhagen Journal of Botany,' 

 t. vii, f. 15, under the name of " Cosmarium Brebissonii, forma 

 genuina, latior et angustior." It is utterly out of the question 

 to identify the very common and easily recognised and very large 



