Juap. XII. TRANSMISSION OF MOTOR IMPULSE. 313 
were beetles,* and out of the whole fourteen there 
was only one, viz. a dipterous insect, which could 
readily take flight. Drosera, on the other hand, 
lives chiefly on insects which are good flyers, especially 
Diptera, caught by the aid of its viscid secretion. But 
what most concerns us is the size of the ten larger 
insects. Their average length from head to tail was 
‘286 of an inch, the lobes of the leaves being on an 
average ‘53 of an inch in length, so that the insects 
were very nearly half as long as the leaves within 
which they were enclosed. Only a few of these leaves, 
therefore, had wasted their powers by capturing small 
prey, though it is probable that many small insects 
had crawled over them and been caught, but had 
then escaped through the bars. 
The Transmission of the Motor Impulse, and Means 
of Movement.—It is sufficient to touch any one of the 
six filaments to cause both lobes to close, these becom- 
ing at the same time incurved throughout their whole 
breadth. The stimulus must therefore radiate in all 
directions from any one filament. It must also be 
transmitted with much rapidity across the leaf, for in 
all ordinary cases both lobes close simultaneously, 
as far as the eye can judge. Most physiologists be- 
lieve that in irritable plants the excitement is trans- 
mitted along, or in close connection with, the fibro- 
vascular bundles. In Dionsa, the course of these 
vessels (composed of spiral and ordinary vascular 
* Dr. Canby remarks (‘ Gar- 
dener’s Monthly,’ August 1868), 
“as a general thing beetles and 
insects of that kind, though al- 
ways killed, seem to be too hard- 
shelled to serve as food, and after 
a short time are rejected.” Iam 
surprised at this statement, at 
feast with respect to such beetles 
as elaters, for the five which I 
examined were in an extremely 
fragile and empty condition, as if 
all their internal parts had been 
partially digested. Mrs. Treat 
informs me that the plants which 
she cultivated in New Jersey 
chiefly caught Diptera. 
