and on a new Species o/" Protococcus. 421 



measured, but sketched and described all the contents of the 

 sporaugial cell, when it further became evident that there was 

 but one large triangular individual present, and that the rest 

 consisted of groups containing eight each of the same form, 

 but of a much smaller size. 



From this period up to the 9th of August (an interval of 

 three weeks) various interruptions prevented my return to 

 the examination of the contents of the gum-bottle ; but at this 

 date, to my surprise, I found similar groups of the unknown 

 Desmid, which I had previously sketched in the sporangium, 

 free (that is, unenclosed in any cell whatever), much enlarged, 

 and very numerous. 



I then turned to Pritchard's '■ Infusoria' (ed. 1861), and in 

 his iirst plate, figs. 57 & 58, found almost identical representa- 

 tions of this organism, which, on refemng to the text among 

 the Desmidie^e, at p. 755, proved to be Sorastrum spinulosuvi 

 Nag., of which it was stated " Propagation unknown," with 

 the letter" G," indicating that it had only been found in Ger- 

 many. Next I souglit for it in Kutzing (Species Algarum, 

 1849), where I found it, at p. 195, constituting a genus, but 

 still placed among the Desmidiea?. Lastly, I consulted Raben- 

 horst (Flor. Europ. Algarum, 1868), where, with figs. no. 38, 

 p. 18, and text p. 81, it is placed among the Protococcaeese as 

 the 49th genus of his Coccophycege. 



Not knowing whence the figures in Pritchard had been 

 taken, or whether Sorastrum had been found in the British 

 Isles, I Avrote on the subject to Mr. AV. Archer, of Dub- 

 lin (whose revision of the Desmidian group in Pritchard's 

 last edition of the Infusoria has so greatly contributed to the 

 success of this useful publication) ; and, in reply, !Mr. Archer 

 stated that the figures were taken from Niigeli's Unicellular 

 Algffi (Gatt. einz. Alg. pi. 5. fig. D, h & d), but that, since they 

 had been copied into Pritcliard, Mr. Archer had seen Sorastrum 

 spinnhsum "many times and in various places in Ireland, but 

 always A'ery scant and sparing." Moreover Mr. Archer kindly 

 presented me with copies of the * Proceedings of the Dublin 

 Microscopical Club ' (preeminent in all matters of this kind 

 for their accuracy and interest), wherein a " brief" description 

 of Sorastrum sjnnidosum is given from specimens exhibited 

 before the meeting of the Chib held on the 21st Sept. 1865, 

 p. 40, and subsequent mention of it again (having been found 

 by the same author) at their meeting held on the 19th July, 

 1866, p. 101. To ]\[r. Archer's description I shall have again 

 to refer hereafter ; meanwhile let us return to the develop- 

 mental history of those specimens of Sorastrum more imme- 

 diately under our consideration. 



