DUBLIN NATURAL HISTORY SOCIETY. 21 



sluggish motion swim about on the water. A gentleman conveisant 

 with microscopic subjects called on me just at the time. I directed his 

 attention to the frustule I had been observing, and he, too, witnessed 

 the phenomenon I have just described. Several frustules, which exhi- 

 bited the abnormal characters as regards the presence of vesicles and the 

 colour of the endochrome, were carefully examined by me, in hope of 

 having an opportunity of observing the extension of the vesicles ; but, 

 although many of these were surrounded by bodies similar in appear- 

 ance, and having the same motion, in no case except the one did I wit- 

 ness the actual issue of them from the cell. This observation, confiinn- 

 atory of the former one, and tending to establish the theory that the 

 Diatomaccse, as well as their kindred organisms, the Desmidiacese, some- 

 times propagate by means of Zoospores, I considered of sufficient impor- 

 tance to induce me to bring it under the notice of the Society. 



The following gentlemen were elected Ordinary Members of the 

 Society : — Eichard William Ormsby Rutledge, Esq., Hague House, Isle 

 of Man ; Octavius O'Brien, Esq., Dublin ; Kichard Dowden (Eichard), 

 Esq., Eathlee, county of Cork. 



FEIDAY EVENING, FEBRUARY 3, 1860. 

 EoBEET Callwell, M. E. I. A., Vice- President, in the Chair. 

 The previous Minutes were read and signed. 

 Me. William Archer read a paper — 



on the occurrence of zoospores in the eamily desmidiaceie. 

 (with a plate.) 



In bringing forward the accompanying drawings, illustrati^s-e of the 

 phenomenon of the production in the family Desmidiaceae of what I be- 

 lieve to be Zoospores, — while I have to express my regret that so many 

 links are wanting in the history of their formation and production, — I 

 nevertheless feel confident the observations will be found, even so far 

 as they go, of abundantly sufficient novelty to warrant my drawing at- 

 tention to them. The sicgular condition which the figures represent 

 seems to be one of such rarity, so far as I can learn, as to lead me to 

 believe that this will be the first time of any similar phenomenon being 

 either figured or recorded in this family — A. Braun's account of what 

 takes place in Podiastrum (I believe not truly a Desmidian at all) ex- 

 cepted. And although I cannot, perhaps, add much to their value by 

 any accompanying remarks of mine, I shall, however, have indicated, as 

 -it appears to me, the direction in which we are to look for, and the 

 mode in which we are to expect hereafter, the production of zoospores, 

 at least in Docidium, which genus furnishes us with the examj/le in 

 question, as well as perhaps in any other Desmidian genus. 



This consideration leads me to believe that, before ofl'ei-ing anything 

 in the way of explanation of the figures, it would be of importance to 



