NOTES AND MEMORANDA. 
375 
necessary, in order tliat tlie diatoms should be desiccated without 
perishing, that they should be enveloped in the mud, and that conse- 
quently the desiccation of these Algae does not take place in the open 
air. M. Petit replied that that was in effect his opinion, and that he had 
remarked in the course of his observations that all the diatoms which 
were in the open air without the intermediary of a protecting body to 
retard the desiccation were dead, and that all his efforts to recall them 
to life were in vain.* 
The Diatomacece of the Arctic Expedition. — Dr. Dickie reports in 
the ‘ Journal of the Linnean Society ’ (No. 98, Bot.) on the Algae col- 
lected during the last Arctic Expedition, by Captain Feilden, Dr. 
Moss, and Mr. Hart, beyond lat. 78° N., including the Diatomaceae. 
The localities where they were gathered are first given in numbered 
series, after which comes a list of all the genera and species, with 
numbers corresponding to the localities attached. This saves need- 
less repetition, is available for data concerning distribution, and at 
a glance shows paucity or frequency of genera and si)ecies. 
The Diatomaceae observed represent thirty-one genera, and amount 
to seventy species ; most of them are marine, the fresh-water species 
being few in number. The presence of these minute organisms, with 
their exquisitely sculptured siliceous investments, is a point of much 
interest in relation to the presence of certain forms of animal life. 
Dr. Dickie has repeatedly received masses of such, resembling pieces 
of fat or of sodden bread, from ice-floes in various parts of the Arctic 
Sea ; and in the alimentary canal of bivalve Mollusca from the same 
quarter preserved in spirits, he has found abundance of marine 
diatoms. 
Where these occur (and they are generally plentiful) this implies 
the possible presence of animal life, the lower forms of which are 
preyed upon by the higher ; and thus we have a very notable and 
interesting chain of dci^jendence. It is not, therefore, a matter for 
surprise that sixteen species of bivalves were collected beyond 80° N. 
by the naturalists of the Expedition. 
P. T. Cleve, in a communication to the Swedish Academy of 
Sciences in 1873, states that the entire number of diatoms found in 
the Arctic Sea is 181 ; the species already enumerated, excluding the 
twelve freshwater, amount to about one-third. From the same paper 
it would appear that those found near Spitzbergen are far more 
numerous than those now recorded. 
Melicerta ringens. — Mr. F. A. Bed well has re-examined the mastax 
with the ^ oil-immersion. His letter to the Secretary will be found 
with the ‘ Proceedings,’ p. 391. 
The Oil-Immersion Objective. — Professor Hamilton Smith con- 
tributes an article on the to the ‘ American Quarterly Micro- 
scopical Journal.’ He “ has no hesitation in saying, and all who have 
looked through it agree with him, that up to this time it is the best 
foreign-made objective he has seen ; ” but, whilst “ begging not to be 
understood as depreciating it,” he maintains, however, that a and 
* ‘ Bull, de la Soc. Bot. de France,’ vol. xxiv. p. 369. 
t ‘ American Quar. Mic. Journal,’ vol. i. p. 28. 
