510 TRANSACTIONS OF SECTION D. 
moderate degree of heat, there are many species which live equally well in 
cold Arctic and Alpine lakes, where the temperature is only a few degrees 
above freezing point, and in the warm lakes of tropical countries. But there 
is no doubt, also, that some species are able, slowly no doubt, to accom- 
modate themselves to much higher temperatures, and Dr. R. Issel has found 
10 species, ordinary kinds, living in hot springs near Padua in Italy, at 
temperatures ranging between 35° and 45° Centigrade. 
On the other hand, in Arctic regions, where all water becomes solid 
during the greater part of the year, the Rotifers, or their eggs, survive the 
most severe frost, and come to life again as soon as the ice melts. Mr. Jas. 
Murray informs me that in the Antarctic regions he found at the bottom of 
a lake on Ross Island, which had been frozen solid for an unknown number 
of years, a layer.of mud containing frozen Bdelloid Rotifers, which re- 
covered and came to life immediately they were placed in water. In order 
to reach this bottom layer Mr. Murray had to make a shaft 15 feet deep 
through solid ice. This, I think, constitutes a record of endurance for 
Rotifera,. 
To account for such a distribution over the whole of the globe, it has been 
supposed that most species of Rotifera can be dried up and their bodies 
carried by the wind, as dust, for long distances, and then come to life 
again on landing in suitable surroundings. This is, however, a very 
erroneous generalisation of the fact that a very few species of Bdelloid 
Rotifera, and in particular Philodina roseola, as first shown by Davis, are 
capable of secreting, when drying slowly, a gelatinous envelope in which 
they can resist drought for many months, and come to life again on 
being placed in water. ; 
This property appears to be confined to the above species and some 
moss-haunting Rotifers of the genera Philodina and Callidina, which 
habitually live on moss that periodically dries up and then becomes wet 
again by rain. Species living in always submerged moss do not appear to 
acquire this property. Another condition of the formation of the protect- 
ing gelatinous envelope is that the desiccation should be slow, otherwise 
it cannot be formed and the animals die in a short time. 
My experience has shown me, and is confirmed by the experiments of 
D. D. Whitney, that the vast majority of Rotifers die immediately on 
being dried and do not revive after complete desiccation, but their eggs, 
and in particular their resting eggs, with more resisting shell, can stand 
a prolonged state of desiccation and also freezing, and can therefore readily 
be transported by the wind or by aquatic birds and other animals, and will 
hatch when deposited in suitable pools of water. 
In my opinion it is by this means that the cosmopolitan distribution 
of the Rotifera over the world has in the course of time been brought about. 
Resolutions. 
(i) The Zoological Section of the British Association wish to record their 
sense of the danger caused by the approach of the Norwegian rat, which 
threatens the wheat industry of Western Canada, and to urge the Govern- 
ments concerned to take immediate steps to organise the extermination of 
this dangerous pest. 
(ii) In view of the enormous importance of the Fisheries of Canada in 
connection with her prosperity and her rapidly developing position as the 
great resource of the food supply of the Empire, and appreciating the 
danger of exhaustion which menaces certain of the Fisheries, the members 
of the Zoological Section of the British Association for the Advancement of 
Science now meeting in Winnipeg, desire to congratulate both the Dominion 
and Provincial Governments upon the work already accomplished in con-, 
