84 
NOTE on SOME HABITS of CRUSTACEA. 
By ALFRED O. WALKER, F.L.S. 
[Read 13th December, 1889. ] 
QNE or two observations which I have made this summer 
in connection with Crustacea may be interesting. The 
first that occurs to me has reference to the common 
Woodlouse or Slater (Oniscus asellus, Linn.). I had 
frequently noticed these animals in my bath in the 
morning, they having fallen in during the night, when 
they were generally alive and creeping on the bottom, for 
(unlike insects) they always sink. I therefore tried the 
following experiment, showing that they can live over 
fifteen hours under water :— 
July 25th, 1889: At 8 a.m. placed an Oniscus asellus in 
a phial 23” deep x 13” diam., wide-mouthed and uncorked, 
filled with river water (clean) nearly to the shoulder. The 
animal sank at once to the bottom, where it walked about, 
occasionally making vain efforts to climb up the side of 
the phial.—7 p.m.: Animal alive, but rather sluggish. 
Poured water off, without uncovering him, to within 
half an inch of the bottom, and again filled up to shoulder. 
Animal quite lively again, walking rapidly about the 
bottom and trying to climb up the side.—11.30 p.m.: 
Animal quite lively, walking about.—July 26th, 7.45 a.m.: 
Animal dead. 
This is very strong evidence in favour of the evolution 
of Oniscus from the aquatic Isopoda, the half-marine half- 
terrestrial Ligia oceanica forming a connecting link. 
An interesting fact, illustrating the ingenuity shown 
by more than one species of Crustacea in concealing 
ee 
