MEMORANDA. 187 
did not altogether harmonise readily with those in balsam. 
Professor Smith, in several letters to me (May to October, 
1853), expressed his inability to form clear conceptions of 
their structure, and begged me to pay particular attention to 
them, and try if I could make it out when engraving them, 
At one time, in the course of correspondence, he writes, ‘“ I 
do not quite understand your views ;” at another, ‘I believe 
you will prove eventually in the right.” 
The subject occupied my thoughts much, and many an 
hour of patient labour was spent in the examination of speci- 
mens. <A mounting of Rhabdonema arcuatum, burnt on talc, 
dry, at length furnished me with the long sought for key to the 
difficulty. Some of the frustules had been burst into their 
components by expansion of the contained air, the pieces, 
however, being left nearly in their relative position. From 
this the analytical figure (‘S. B. D.,’ pl. xxxviu, fig. 305+) 
was engraved, and on receipt of the proof Professor Smith 
expressed in warm terms his satisfaction with the result, and 
as we laughed over it we wondered it could ever have ap- 
peared difficult. Had the briefest acknowledgment been made 
in the ‘Synopsis’ that the discovery was mine I had been 
amply repaid the trouble and time spent over it, and should 
have been spared the very unpleasant task of writing as I 
have felt obliged to. The appearance of the second volume of 
the ‘ Synopsis’ without the promised acknowledgment pained 
me much, but the friendship that had existed between Pro- 
fessor Smith and myself prevented open mention of the in- 
justice done me, on which, as I hope at a future day to write 
on the Diatomacez, I should not have made the present 
remarks, but that the subject was mentioned in the last part 
of the ‘Journal’ in amanner which compels me to do so with- 
out further delay. The interesting specimen which furnished 
the clue to the mystery is still in my possession, and I shall 
be happy to show it to any who take an interest in the sub- 
ject. Striatella, Tabellaria, Tetracyclus, and Grammato- 
phora, after the light thus afforded, no longer presented any 
difficulties. 
It was with great satisfaction I succeeded, after much time 
and patient thought, in resolving the structure of Rhizoso- 
lenia, so neatly and pithily described by Mr. Brightwell, in 
the last part of the ‘ Journal.’ In the possession of “ annuli,” 
and in the indefinite increase of the frustule before self- 
division, this genus must undoubtedly in a natural classifica- 
tion be placed near Rhabdonema, &e. From all which, 
however, it differs in the non-possession of septa, in any of 
the several modifications now known. The extreme obliquity 
