6 NOTES AND COMMENTS [sULY 
Bryozoa and Bipolarity. 
Str JOHN Murray may take heart again. His attempt to explain 
the similarity between the north and south temperate faunas has 
been met by more that one specialist (even among those quoted in 
support of his argument) by a denial of the similarity, at all events 
to the extent assumed by the bipolar hypothesis. But now comes 
a lady to defend the knight. Miss Edith M. Pratt, of Owens 
College, Manchester, has been studying some collections, chiefly of 
Bryozoa, made on the shore of the Falkland Islands (Manchester 
Memoirs, vol. xlii. No. 13, 14th December, 1898). After a careful 
analysis of the distribution of the genera, she concludes that the 
results “as far as Bryozoa are concerned, seem to support Murray’s 
theory.” “Each genus represented in the collection occurs fossil, and 
also occurs in the north and south temperate zones, as well as in the 
tropics; in fact most of the genera are cosmopolitan. Many of the 
species are represented in the Tertiary deposits. This shows that the 
changes of ¢limate and the altered conditions of life have not affected 
their ‘ Tertiary ’ structure ; as many of these forms occur only in the two 
temperate zones, there is reason to believe that they have retained 
their common ancestral structure. The fact of many of the species 
occurring in the deep sea hardly supports Ortmann’s theory [that an 
exchange of polar forms can take place through the deep sea], for 
many of them occur at very great depths only in the temperate 
regions ; in the ¢ropics they occur in shallow water. Their presence in 
the deep sea is, I think, the result of accident.” 
It is pleasing to find some attention paid to distribution in former 
geological periods; but does Miss Pratt, or can Sir John Murray, 
suppose that what took place in Tertiary times has much bearing on 
the question? It cannot seriously be maintained that there was any 
appreciable difference of world-temperature so recently as the Tertiary ; 
certainly there was no approach to a universal climate in those days. 
We have to go back a good deal farther before our facts can bear any 
relation to the primal temperature of the globe. If there be a 
similarity between the present polar faunas, we do not see how any 
identity of species can be due to events that took place, if at all, 
in early Palaeozoic ages. As for certain cases of distribution being 
“the result of accident,” what can Miss Pratt mean? It is too easy a 
way of explaining inconvenient facts. 
Miss Pratt also studies the distribution of Anthomedusae, Porifera, 
Polychaeta, Gephyrea, Mollusca, Echinoderma, Crustacea, and Tunicata. 
Out of twenty-four species, three have been recorded from north and 
south temperate regions only; one from north and south temperate 
regions and the tropics; one from tropics and southern hemisphere ; 
and all the rest from the southern hemisphere only. These facts 
scarcely show a striking similarity between the temperate faunas of the 
