102 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
In the Amphipoda Gammaridea of ** Das Tierreich ” 
the above species are placed together, with the exception 
of an Arctic form, V. brevicornis (Sars), which is placed 
between V. monocuspis and NV. assimilis. It, therefore, 
we are to consider them as three distinct species, what 
becomes of the “axiom” or “law”? For it can hardly 
be pretended that there is any such “ barrier” in a hole 
half a mile long by 300 yards wide as would suffice to 
separate two species! But as regards V. monocuspis, I 
ventured in the * Revision of the Amphipoda of the 
L.M.B.C. District ’* to express my opinion that it was 
only the immature form of V. bécuspis—an opinion since 
strengthened by the discovery of an Antarctic species, 
Oradarea longimana, A.O.W.,t in which a_ precisely 
similar difference between old and young individuals 
(viz., the absence of the postero-dorsal tooth on the second 
pleon segment in the young) exists. But even if my 
view be accepted, there still remains the cohabitation of 
two certainly distinct but nearly allied species to be got 
over by the supporters of the above “ law’’! 
On the other hand, I entirely agree with Dr. 
Herdman’s view} that species of the same genus among 
marine animals are rarely found associated, and I regard 
the above instance as exceptional, though I took the same 
three (or two) species together in the same place in April, 
1894. 
Norr.—Since the above was written it has occurred 
to me that I have dredged Corophium crassicorne, Bray, 
and C. bonelli, M. Edw., in the same hole off the Little 
Orme, thouga not at the same time—the former having 
been taken in October and the latter in August. This is 
an important difference, as it 1s quite possible that the 
two species may never be together, many Amphipods 
being known to be migratory.—A. O. W. 
* Trans. Liverpool Biol. Soc., Vol. 1X, 1895, p. 303. 
t Journ. Linn. Soc. Zool., Vol. XXIX, p. 56. 
t Trans. Liverpool Biol. Soc., Vol. X, 1896, p. 56. 
