192 PROCEEDINGS OF SOCIETIES. 



all being alike, except of course where interstitial growth of new 

 semi-cells might be going on, in the ordinary characteristic man- 

 ner. It needs not, therefore, to point out that this attachment 

 by a gelatinous cushion-like stipes is in no way comparable to the 

 mode of attachment of young conjugate forms by means of a 

 "root-cell ;" the basal cell as mentioned does not form a " root- 

 cell" by any means, but is quite equivalent to each and all of the 

 remainder of the perfectly independent cells going to make up 

 the " filament." Indeed, in this genus, destitute of any little 

 connecting processes between the concatenation of cells charac- 

 teristic of Sphaerozosma, it is probable that the cells are mutually 

 held together by a very short intervening gelatinous pad, com- 

 parable to, but much smaller than, the stipes by which the whole 

 is attached to foreign objects. 



Optio Vesicles in Chick. — Dr. Macalister exhibited for Prof. Cle- 

 land a mounted preparation of ayoung'chick aboutthirty-six hours 

 old, showing the condition of the optic vesicles at that stage. 



Exhibition of rare (some very striking^ Desmidian Species. — 

 Mr. Archer exhibited a number of exceedingly rare Desmidiese 

 from a recent gathering made in Connemara, including the 

 (so to speak) colossal forms of Staurastrum : St. arctiscon (Ehr.) 

 Lundell, St. ophiura, Lundell, ^S*^. sexangulare, Bulnheim, ^S*^. 

 longispinum, Bailey ; other not less rare and interesting forms, if 

 smaller and less striking than these fine objects, occurred in this 

 rich collection. 



IQtl November, 1876. 



Odontodiscus Hihernicus, O'M., exhibited. — Rev. E. O'Meara 

 exhibited a slide of diatoms taken from stomachs of Ascidians 

 cast up by recent storms on the shore of Dublin Bay. Several 

 forms of interest occurred in the material, and especially 

 Odontodiscus Hiiernicus, O'M., a new species described by Mr. 

 O'Meara in his ' Report on Irish Diatomaceae' (' Proc. R. I. 

 Acad. Science,' ser. 2, vol. ii, p. 271, pi. 27, f 7). 



Roots of JJtricularia montana, exhibited. — Dr. Moore exhibited 

 roots of the South American JJtricularia montana. The roots 

 exhibited had grown over the margin of a flower-pot in which 

 the plant is cultivated in one of the conservatories at Glasnevin, 

 and were clinging to the bare exterior of the pot. Notwith- 

 standing they were beset with miniature bladders, as perfectly 

 formed as those on our British species, though these were scarcely 

 perceptible to the unaided eye ; when viewed through a three- 

 quarter-inch objective, they are both pretty and curious objects. 



Transverse section of the Spine of Porocidaris purpurafa, Wy. 

 Thomson, was exhibited by Mr. Mackintosh ; the section, 

 however, did not present as remarkable features in its internal 

 structure as one would have expected from the striking external 

 appearance of the species. Its principal peculiarity was the 

 very slight external crust, which had simple tubes traversing it. 



