382 
acquaintance between investigators pursu- 
ing related lines of research; it has made 
each Association better acquainted with the 
character and purposes of the other; it has 
increased mutual esteem between the men 
and institutions; and it strengthened both 
bodies in attendance and in quality and 
quantity of work, and has been especially 
beneficial in diffusing knowledge of and 
interest in scientific matters among the 
people of two countries. Some of the bene- 
fits were felt at the meetings; yet it seems 
fair to regard these as but the germs of 
greater benefits to come as the personal 
and collective relations begun at Detroit 
and Toronto mature and strengthen. 
Ié seems specially desirable to note the 
international amenities characterizing the 
Detroit and Toronto meetings, since minor 
misapprehensions have come to the surface. 
For example, it has been alleged in the 
newspapers that certain members of the 
American Association were treated with 
discourtesy at the Toronto meeting. It 
must be evident, in view of the prevailing 
harmony and the unprecedented warmth of 
the courtesies extended by each of the As- 
sociations, that the sources of individual 
eriticism are to be found in personal mat- 
ters and not at all in general feeling. It 
may not be amiss to add that the Local 
Secretary of the British Association has ex- 
plained, through the public press, that cer- 
tain Americans, who complained, through 
the medium of associated press despatches, 
of discourtesy at Toronto, were not regis- 
tered as members of the British Associa- 
tion, and therefore occupied the precise 
footing of the general public, which, in the 
British Association, is not entitled to ad- 
mission to the meetings or other participa- 
tion in the work of the body. The great 
and significant fact is that the relations be- 
tween the two Associations at Detroit and 
Toronto were most cordial, sympathetic 
and beneficial; this fact assuredly over- 
SCIENCE. 
[N. S. Vou. VI. No. 141. 
shadows any and all petty misapprehen- 
sions, and must serve to render the meet- 
ings memorable. 
W J MoGer. 
THE SPREAD OF LAND SPECIES BY THE 
AGENCY OF MAN; WITH ESPECIAL 
REFERENCE TO INSECTS. 
Amone the many influences which dur- 
ing the last century or two have been affect- 
ing that unstable condition of life which is 
expressed in the words ‘the geographical 
distribution of animals and plants’ none 
has approached in potency the agency of 
man exerted both purposely and unwit- 
tingly or accidentally. 
Natural spread was for centuries the rule. 
Species dispersed under natural conditions 
along the line of least resistance. Winged 
animals and seeds were spread by flight 
and by the agency of winds, and at their 
stopping places thrived or did not thrive 
according as conditions were suitable or 
not suitable. Aquatic animals and plants 
and small land animals and plants were dis- 
tributed by the action of rivers and streams 
and by the ocean itself. Wonderful migra- 
tions have occurred, commonly with birds, 
more rarely with other animials; ice floes 
and driftwood have carried animals and 
plants far from their original habitats and 
even volcanic action has taken part in the 
dispersal of species. Smaller animals, espe- 
cially mollusks and insects, and the seeds of 
plants have been carried many hundreds of 
miles by birds and lesser distances by mam- 
mals. 
With the improvement of commercial in- 
tercourse between nations by land and by 
sea another factor became more and more 
prominent, until in the present period of 
the world’s history the agency of man in 
the spread of species, taking all plant and 
animal life into consideration, has become 
the predominating one. Potentially cos- 
mopolitan forms, possibly even insular in- 
