ZOOLOGY. 631 
tissues harden, and we can then withdraw from the acid solution 
the objects which have been submitted to its action, wash them 
carefully several times, and then place them in strong alcohol 
without running the risk of finally destroying either their elegant 
forms or the transparence of their tissues. We can even after 
several weeks, and probably after several months, study the organ- 
ization and the structure of these delicate beings as well as if we 
had them living under our eyes. 
Another method that I have employed with success consists in 
the use of picric acid in a concentrated aqueous solution. I have 
preserved in this liquid, for about six weeks, small Meduse 
(Oceania) and Noctiluce. We only notice that the small Meduse, 
which are perfectly transparent in life, have become plainly 
Opaque. I have examined microscopically some Noctiluce thus 
preserved, and can state that they appear just as they i came from 
the sea.— E. Van BENEDEN. 
Tue Avı-FAUNA or Cororapo.— Dr. Coues, in the June number 
of the Naruratist, criticises the Holden-Aiken list of the Birds of 
Colorado. So far as his criticism has any pertinence, it would 
seem to be to complain of the incongruity of grouping in the same | 
list birds found in northern and in southern portion’ of this terri- 
tory. If this were the first time that local lists were made, based 
on political and disregarding natural lines, it would perhaps be 
worth while to discuss this point. Or I might fall back upon my 
reserved rights, and, while allowing to my critic the full right to 
his individual opinion, claim the right to differ, toto celo. Or I 
might cite, in extenuation of my offence, a well known list of New 
Ehglind Birds, in which “ such birds as” the hooded warbler and 
the Canada jay “find themselves in ornithological company they 
never saw outside of a book—” or that of the birds of Arizona, 
or of South Carolina wherein similar forced associations are only 
Possible cum longo intervallo. But my transgression is one for 
which I propose to make no excuse, and for which I do not need 
even such illustrious examples; and I would not now have re- 
ferred to this critique but for an unfortunate error which I deem it 
important to set right. Facts are more valuable than mere 
Unsupported theory, and illustrations are peculiarly unfortunate 
when they contradict instead of confirming an hypothesis. Such 
is the case with my critic. To demonstrate the impropriety of the 
