DUBLIN MICROSiCOPICAL CLUB. 431 



under his dark ground illumination (such as Navicula rhomhoides, 

 &c.)j the whole of the strire being brought out with extremely 

 clear precision. 



Mr. Archer exhibited examples of three very "closely allied" 

 and much resembling minute forms of Cosmarium, two of these 

 in the conjugated condition, pointing out Ealf's figure of the 

 zygospore of the third [Cosmarium tinctum), for the purpose of 

 showing how amongst Desmidie^, the mature form of certain 

 species may so closely resemble each other, but yet possess 

 extremely different zygospores ; no doubt, indeed, the converse is 

 not rarely true, that is, that certain species may ofier very 

 tangible and even strong differences inter se, yet possess zygospores 

 mutually very closely resembling each other. One of the forms 

 now in question was Cosmarium tinctum (Ralf's), of which he could, 

 not find a conjugated specimen on the present occasion, Cosmarium 

 temie (ejus), ' Quart. Journ. Micr. Sci.,' N. S., vol. viii, p. 293), and 

 the third a new species ; of these the first has a subquadrate, or 

 polyhedral smooth light-coloured zygospore, the second a large 

 globular brown-coloured (when mature) zygospore, the third an 

 irregularly figured variously lobed zygospore, the lobes surmounted 

 by generally a pair of short tapering subacute spine-like processes. 

 The last had thus a zygospore resembling that of Cosmarium 

 lolatosporum (Arch., in 'Quart. Journ. Micro. Sci.,' vol. xv, N. S., 

 p. 171), but then the mature form is quite dissimilar. It will 

 not be assumed that of the three related species now exhibited 

 the mature forms were not appreciably distinct, for, when the 

 eye gets accustomed to them, their difterences are in reality quite 

 observable; still they might be° easily passed over the one 

 io¥ the other, in the unconjugated state. Neither Cosmarium 

 teiiue nor the above-referred-to new one appears to occur in Sweden, 

 but, as to be expected, Lundell includes C. tinctum in his enume- 

 ration. 



Eev. E. O'Meara exhibited from Capt. Chimmo's prolific 

 Diatomaceous gathering from Sulu, a further new Navicula to be 

 hereafter named N. vertehrafa. 



Dr. Erazer showed a fine Photograph of scale of Degeeria 

 domestica executed by Colonel Woodward of the United States 

 (with a Powell's -^^), and forwarded by that gentleman. 



Dr. Eichardson exhibited some further mountings by Mr. Baker 

 of London, one of the spicules of Hyalonema mirahile (not as on 

 the last night of meeting on separate slides, but) showing the 

 three forms geometrically arranged, in such a way that at each 

 corner of the figure there is a multihamate spicule, in the centre of 

 the cylindro-cruciform spicules, with densely spiculate shafts, as 

 well as having the shafts smooth and the ends spiculate. Dr. 

 Eichardson also showed Plagiogramma elongatum and Actinocyclus 

 RaJfsii, both being exquisite mountings of Mr. Baker's. Dr. 

 Eichardson showed, lastly, a transverse section of the spinal cord 

 of the cat, surrounded by transverse sections of its membranes ; 

 the specimen was taken from apiece of the cord hardened accord- 

 ing to Mr. Lockhart Clarke's method and subsequently stained 



