t86 
The Nattirahst in La Plata, 
far out at sea, it is difficult to believe that sucli 
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 J; 
highly developed, but the elementary feeling, out of 
which the wonderful habit of the swallow has q 
grown, exists widely throughout animated nature. jj 
On the continent of Europe it also seems probable U 
that a great autumnal movement of these spiders ij 
takes place ; although, I must confess, I have no 
grounds for this statement, except that the floating h 
gossamer is called in Germany Der fliegender 
Summer ” — the flying or de]3arting summer. ^ 
I have stated that all migrations of gossamers I h 
have witnessed have been in the autumn ; except- I 
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 a stream 
