186 The Naturalist tn La Plata. 
far out at sea, it is difficult to believe that such 
migrations take place. But where they inhabit a 
vast area of land, as in South America, extending 
without interruption from the equator to the cold 
Magellanic regions, and where there is a long 
autumn of dry, hot weather, then such an instinct 
as migration might have been developed. For this 
is not a faculty merely of a few birds: the impulse 
to migrate at certain seasons affects birds, insects, 
and even mammals. In a few birds only is it 
highly developed, but the elementary feeling, out of 
which the wonderful habit of the swallow has 
grown, exists widely throughout animated nature. 
On the continent of Europe it also seems probable 
that a great autumnal movement of these spiders 
takes place; although, I must confess, I have no 
grounds for this statement, except that the floating 
gossamer is called in Germany ‘‘ Der fliegender 
Summer ’’—the flying or departing summer. 
{ have stated that all migrations of gossamers I 
have witnessed have been in the autumn; except- 
ing in one instance, these flights occurred when the 
weather was still hot and dry. The exceptionally 
late migration was on March 22—a full month after 
the departure of martins, humming-birds, fly- 
catchers, and most other true bird-migrants. It 
struck me as being so remarkable, and seems to 
lend so much force to the idea I have suggested, 
that I wish to give here an exact copy of the entries 
made at the time and on the spot in my notebook. 
**March 22. This afternoon, while I was out 
shooting, the gossamer-spiders presented an ap- 
pearance quite new to me. Walking along astream 
