DUBLIN MICROSCOPICAL CLUB. 3i9 



series, though indefinitely scattered in the stems, and, in E,ivu- 

 laria, like tlieni destined to become removed and serve to the 

 vegetative propagation of the plant. Such a mode of vegetative 

 growth doea not appear to have been noticed in Rivularia. 



Some Arctic Diatoms, amongst lohich Biddulpliia Balcena, 

 which ap-pears rather to he a Trineratium. — Rev. E. O'Meara 

 showed a slide containing Diatoms, collected in Franklin Bay by- 

 Major Fielden, R.A., "Naturalist to the Arctic Expedition. The 

 collection is a most valuable one, containing numerous rare 

 species, amongst which are to be found Coscinodiscus punctatus, 

 Greg. ; Synedra Kamskatica, O'M. ; GramiT.atophora arctica, Cleve; 

 Hhahdonema TorelUi, Cleve ; Pleurosigma longum, Cleve ; Thal- 

 lasiosira Nordskioldii, Cleve ; Wwiconema hollinana, Grunow ; 

 Triceratium arcticum, Brightwell ; Biddulphia Balcena, Bright- 

 well. To this last Mr. O'Meara directed special attention, and 

 expressed his opinion that it would be more properly included in 

 the genus Triceratium. Except as regards its somewhat rhom- 

 boid outline the characters closely resembled Triceratium arcti- 

 cum, with which it was not unfrequently associated. 



2lst March, 1878. 



VerricTc's ^th. — Mr. Eichardson drew special attention to the 

 excellence of this objective. It was the power (about -Jth) supplied 

 by Verick with his low priced stand, and defined so well that he, 

 ]\Ir. Eichardson, preferred it for demonstrating most sections to 

 glasses of some other makers of about the same power in his 

 possession, each of which cost considerably more than Verick's 

 stand and its two objectives. Moreover, the glass without any 

 special arrangement therefor, acted equally well whether as a dry 

 or as an immersion lens. 



Structu7'e of Spine of Echinus acutus, Lamk. — Mr. Mackintosh 

 exhibited a cross section of the spine of Echinus acutus, Lamk. 

 The specimen from which the spine was taken was dredged off 

 the coast of Toughal by the late Dr. Ball, who described it 

 under the name of Echinus Flemingii, but A. Agassiz, (' Eeview 

 of the Echini,' 1872), has placed it as a variety only of Lamarck's 

 older species. The example was presented by Dr. Ball to the 

 Museum of Trinity College, Dublin, and Mr. Mackintosh was 

 indebted to the kindness of Professor Macalister, the present 

 Director, for the opportunity of examining the structure of the 

 spines. They present in cross-section the usual axis of reticular 

 tissue surrounded by four cycles of solid wedges, separated from 

 each other by spokes of trabecular tissue. The cycles might be 

 described as being produced by the constriction at intervals of 

 a single elongated wedge, such as is seen in the spine of the 

 allied E. esculentus, Linn., a section of which was shown for sake 

 of contrast. 



Lafoea fociUum, exhibited. — Mr. Grant showed Lafoea pocillum, 

 one of the Campanularians, of considerable rarity, Hiucks, in his 



