94 JOURNAL OF THE [OctobCT, 



somewhat different from that of the description of this Desmid, 

 given by Carpenter and Hogg.' 



These authors state that the divisions are made in the follow- 

 ing order, i, 3, 5, 7 and 13, and that it takes place in about 

 three and one-half hours. 



Now, the time occupied by my specimen in multiplying from 

 5 to 7 was three-quarters of an hour, but, if I have been clear in 

 my description, the enlargement and subsequent division of No. 

 3 (Figs. 2 and 4) must have continued, and have been com- 

 pleted, before 2 and 2a. (Fig. 4) could have undergone the same 

 process. 



This being the case we should have had i, 2, 2a, 3, -^a, (Fig. 

 5), or nine processes in all, or in other words, one more stage 

 than is described by the authors referred to. 



Both, however, seem to have drawn their inspiration from a 

 paper read by E. G. Lobb, before the Microscopical Society of 

 London — not then Royal, — in 1861, and hence their descriptions 

 agree. 



For many years, I had the pleasure of being personally 

 acquainted with Mr. Lobb, and, having spent many hours in 

 his company, I knew him to be a careful observer. 



I am therefore at a loss to account for the discrepancy. 



One other fact makes it still more difficult, and that is, if you 

 allow three-quarters of an hour for the divisions, and assume 

 them to be i, 3, 5, 7, 9 and 13, you have exactly three and one- 

 half hours. 



On the 20th of June I placed ten or twelve specimens in a 

 special tank for the purpose, if possible, of solving my difficulty. 

 But although I examined them almost every evening for two 

 months, and could see their numbers increase to about forty, 

 and could frequently perceive them in the last, or almost com- 

 pleted stage, I have not been fortunate enough to see the begin- 

 ning, or the middle stage. The denticulation does not appear 

 with the division of the lobes, but is probably coincident with 

 the enlargement of the newly-formed portion of the desmid, 

 which is not at first so large as the original. 



* This species is also described as M. rotata (Grev.) Ralfs by Wolle and Cooke. 



