214 On the Polyzoa of Queen Charlotte Islands. 
bathe the shores of the Queen Charlotte Islands they evi- 
dently find a congenial home and are finely developed. 
There is nothing to show that they are unfavourably affected 
by the change of climate. Of these northern forms only one 
seems to reach the Mediterranean ; a few are widely distributed 
in the British seas, while the rest are pretty much confined to 
Shetland and the north-east and north-west coasts. In Prof. 
Verrill’s ‘Check-List of the Marine Invertebrata of the 
Atlantic coast, from Cape Cod to the Gulf of St. Lawrence’ 
(1879) thirty-one species are included which occur in the 
(Jueen Charlotte Islands, and of these nineteen are Arctic; so 
that the results of the northern migration have been much the 
same on both sides of the continent. 
The remaining species obtained by Dr. Dawson constitute 
a somewhat miscellaneous company. They include a small 
group of cosmopolitan forms which occur in almost all lati- 
tudes, and are expected, as a matter of course, to be present 
wherever Polyzoa are found. Such are Microporella ciliata 
(perhaps the most widely distributed species in the class), 
Schizoporella hyalina (which almost equals it in this respect), 
Smittia trispinosa, and perhaps Hippothoa distans. A few 
species occur which have been found as far up the Pacific 
coast of America as California and Vancouver Island, but 
which are not known as Arctic forms. These are no doubt 
southern species which have travelled so far northwards. 
Indeed the Queen Charlotte Islands are, in a remarkable 
degree, the meeting-ground of northern and southern forms. 
Membranipora Rosselii, M. tenutrostris, Cribrilina radiata, 
Schizoporella Cecilit, S. sanguinea, S. torquata, and Diastopora 
suborbicularis are essentially southern. 
Seventeen species are common to the Islands and Australia, 
and of these thirteen are also Kuropean: nine of them occur 
in the Arctic seas. ‘Two have only been found, so far, in 
Avstralia and the Queen Charlotte Islands (Porella marsupium 
and Mucronella spinosissima). Lepralia cleidostoma has oc- 
curred in these two localities and off the coast of Florida. 
It may be noted here that of the whole number of Queen 
Charlotte Islands species only nine are not also European. 
Some of the ascertained facts respecting the distribution of 
the Polyzoa are sufficiently perplexing, and we must wait for 
a larger accumulation of data before we may hope to explain 
them satisfactorily. ‘The way in which certain species are 
strewn, as it were, at haphazard over the surface of the globe 
is a difficulty of which the solution is not apparent. We must, 
I think (as I have suggested before), make large allowance 
for the agency of man, and of currents, floating weed and 
