TRANSACTIONS. 



On the Self-division of Micrasteiiias denticulata. 



By Mr. Lobb. 



(Read October lOth, 1860.) 



In the month of April last,, Dr. Millar, Mr. Mummery, 

 and myself, went out collecting in Epping Forest, near High 

 Beech, where the Doctor has a residence ; and he being well 

 acquainted with the localities, we soon filled our bottles with 

 Volvox globator, Volvox aureus, Actinophrys sol and viridis, 

 DiiHugia, Floscularia, Diatomaceae, Desmidiaceai, &c. And 

 I may here take the opportunity of saying, that I know of 

 no place so prolific in microscopic gatherings as Epping 

 Forest, which exceeds even the noted bog at Fisher's Castle, 

 Tunbridge Wells. On examining, the next morning, the 

 Desmidiacese, I was favoured with a beautiful view, from com- 

 mencement to termination, of the self-division of Micras- 

 terias denticulata, occupying altogether three hours and a 

 half; the result was to make me feel that Mr. Ralfs is wrong 

 in the figure he gives of the same in his highly valuable work 

 on the British Desmidiaceae (fig. 1, pi. 7). So humble an 

 individual as myself may well pause on difl'ering from so high 

 an authority, but in this instance I am compelled to do so, 

 and am happy to say that I am not alone in so doing, Mr. 

 Tomkins and Dr. Millar having both witnessed the same, 

 and both of them perfectly agree with me. Mr. Tomkins 

 saw it first, myself next, and lastly Dr. Millar. 



The self-division commences by the exudation of a small, 

 perfectly hyaline, membranaceous globule from each half- 

 frustule ; very soon a small portion of granular endochrome is 

 seen issuing forth into the globules from the original half- 

 frustules. (See PI. I, fig. 1.) 



The next stage exhibits the globules dividing into three lobes, 



the endochrome increasing in quantity, sometimes gradually 



extending itself as in fig. 2, and sometimes entering, as it 



were, in two streams from the thickened sides of the end 



^ lobes of the parent half-frustules, as in fig. 3. 



In the next stage the three lobes divide into five; the 

 end lobe remaining mialtered in figure, and only increased 

 in size. (See fig. 4.) 



VOL. I, NEW SER. a 



