ORIGINAL COMMUNICATIONS. 



On the Occurrence o/Zoospores in the Family Desmidiace^e. 

 By William Archer. 



(Read before the Natural History Society of Dublin, Friday Evening, 

 February 3, I860 ; extracted from the ' Natural History Review and 

 Quarterly Journal of Science,' for July, 1860.) 



In bringing forward the accompanying drawings, illustra- 

 tive of the production in the family Desmidiacese of what I 

 believe 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- 

 attention to them. The singular 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 

 Pediastrum (I believe not truly a Desmidian at all) excepted. 

 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 here- 

 after, the production of zoospores, at least in Docidium, 

 which genus furnishes us with the example in question, as 

 well as perhaps in any other Desmidian genus. 



This consideration leads me to believe that, before offering 

 anything in the way of explanation of the figures, it would be 

 of importance to draw attention to what is stated in books 

 on the subject of the occurrence of zoospores in this family. 

 I believe every writer in our text-books on microscopic 

 organisms, when touching on Desmidiacese, states it as a fact, 

 that, like various other algse, they are propagated by zoo- 

 spores ; while some go more or less into details, I am in- 

 duced to say, very deferentially, that I think the descriptions 



VOL. VIII. s 



