120 
OwENj on the Surface-fauna of Mid-ocean. 
iovQ, be the same species."^ It will be satisfactory to have 
more specimens of this from the Pacific, as we all know how 
an error might creep in, in labelling each specimen, when the 
collector passed over so many oceans during the same voyage. 
I have seen the ship^s decks running with liquid fire Avhen 
the net containing this species has been taken on board. I 
must again express my regret that I had no spectrascope 
with me on my last voyage. I am therefore unable to lay 
before you the drawings of the spectra of the luminous 
Entomostraca that are on the table. I shall conclude by 
hoping that some of my zealous fellow- workers will take up 
the subject, and at an early day make up for my want of 
opportunity. It will end in more than a few interesting ex- 
periments. I look for results that may not only add to our 
chemical knowledge, but to such as may afford us some hints 
on matters that are at least the nearest akin to the nature of 
organic life. 
* The difference in the form of the beak has since made nie think it may 
be found entitled to be considered a distinct species. — S. li. I. 0. 
ERHATUM IN CAPTAIN MITCHELL'S PAPER ON THE 
SCREW MICROMETER. 
Page 71, line 3 from bottom. 
Fur — "With nj micrometer a negative eye-piece (one by Powell and 
Lcalnnd), witii four filaments, amounts to the divisions of the micrometer 
head." 
Read — " In my micrometer a negative eye-piece (one by Powell and 
Lcaland), the thickness of one filament is equal to two divisions of the 
micrometer head." 
