22 MEMORANDA. 



Conjugation of Diatomacese. — I have had a large stock of 

 Navicula amphishmna, in several gatherings^ this summer from 

 the Thames, at Weybridge, and have three times distinctly 

 witnessed the follo^ying phenomenon, viz., what I suppose to 

 be the formation of a sporangium by the joint conjugation of 

 three and four frustules, as in Cosmariuni, and some other 

 species of Desinidiacce, 



The frustules, three in two cases and four in the other, 

 were attached to the sporangium by a short stipes proceeding 

 from the centre of the lateral suture of each. 



In two of the cases the endochrome had been discharged 

 from all ; the frustules in the third, in which four frustules 

 were attached to the sporangium; one retained the en- 

 dochrome, which entirely filled the lorica, and was of higher 

 colour, and more condensed appearance than is presented by 

 the species in its ordinary aspect. 



Is it possible this frustule may have been antheridial? 

 This is only an idea. 



The sporangial frustule M^as marked in a series of nodules 

 not unlike in appearance — though but just discernable with 

 Ross's i-inch — the cells of a section of Echinus spine. 1 had 

 not the good fortune to trace the development of the sporan- 

 gium, having only seen it apparently near its perfection, nor 

 have I, in consequence of leaving Weybridge, and my stock 

 having been inadvertently thrown away, been able to follow 

 its further history. — Thomas Charles Druce, Chelsea. 



