10 NOTES ON 
the other extremity, where they meet and 
terminate. During the progress of these air 
tubes they send off numerous ramified branches, 
as displayed in the engraving. The inner pair 
of vessels commence at the ganglia, and lose 
themselves in the third segment from the tail. 
In the penultimate annulus is situated the 
pulsatory organ, which by some zootomists is 
considered to be the true heart of insects, but, 
from the examination of Cuvier and others, it 
appears to have no communication with the 
main vessels of the insect, and hence cannot be 
an organ for circulation. It is termed by him 
the “ dorsal vessel,” and its function, according 
to Marcel de Serres, is the secretion of fat, 
which is afterwards elaborated in the adipose 
tissue that envelopes it. 
To the under-side of the thorax are attached 
six transparent crustaceous legs, marginated 
with fine bristles, placed at short intervals, and 
having strong spines at their articulations. 
They are also terminated by strong ciliated 
claws, and a delicate ramified vessel runs 
through their whole length; the tail is com- 
posed of two processes or spines, having several 
smaller ones branching from them. When one 
of the larger spines is destroyed, I have ob- 
