326 PSTKCHE. 
Agrion puella, are very delicate, and 
extend, in the antennae, mandibles and 
maxillae, from the upper to the lower 
chitinous walls. In no case have I ob- 
served corpuscles of blood pass through 
these porous partitions, but they may_ 
not be impervious to the fluid portion 
of the blood. 
currents of blood and to cause it to cir- 
They serve to guide the 
culate in the appendages. It is not 
necessary for these porous partitions to 
extend into the apical joints of each ap- 
pendage, the blood which fills these 
joints not needing rapid changing. Ca- 
rus notes that, in the larva of Ephemera 
vulgaris, the blood has a distinct outward 
and return current in the basal joint of 
each antenna. This is the case, as will 
be seen by the figure, in the antennae 
of the larva of Hydrophilus, where the 
partition between the two streams ends 
just posterior to the distal end of the 
basal joint of each antenna. 
Verloren? notes that, in the antennae 
of the larvae of Ephemera diptera he had 
never been able to observe the circula- 
tion of the nutrient fluid, except in the 
first joint, where the current enters on 
the inner side and returns on the outer 
side. The direction and extent of 
the currents of blood in the antennae 
are the same in the larva of Ephemera 
diptera as in that of Hydrophilus, but, 
as the literature at my command fails to 
give the necessary data in regard to the 
currents of blood in the antennae of 
other insects, and I have not been able 
to obtain specimens suitable for further 
observation, it is unsafe to predict that 
2 Verloren, M.C. Mémoire en résponse ala question 
suivante: Eclaircir par des observations nouvelles le 
phénoméne de la circulation dans les insectes .. . 1844. 
the currents of blood in the antennae of 
insects generally follow a similar course. 
It will be seen, at first glance, on the 
figure, that, with one exception, all the 
streams of blood have their outward 
course on the inner side of each appen- 
dage; the exception is in the maxillae, 
where the outward course of the blood 
is on the outer side. It would be inter- 
esting to know if, in other insect larvae, 
the streams of blood entered the max- 
illae on the outer and returned on the 
inner side. 
As the circulation in the appendages 
of the head’ of the larvae of Hydrophilus 
has no capillaries, the progress of the 
blood is so little checked that one can 
count the pulsations of the heart as well 
in the returning currents as in the out- 
going ones. 
For the purpose of detailed study of 
the circulation of the blood, not only in 
the antennae and trophi but in all parts 
of the body, the young larvae of Hydro- 
philus offer special advantages, on ac- 
count of their transparency. which is so 
great that their blood-corpuscles can be 
readily seen, under the microscope, 
without using extremely high powers. 
The egg-cases of Hydrophilus can be 
collected in summer,® and the larvae 
easily reared in a small aquarium. If a 
suitable aquarium be chosen, and placed 
beneath any kind of a fly-trap, in such 
a way that the flies captured will fall, 
living, into the water, a healthy brood of 
larvae of Aydrophiius can be fed with 
a minimum of attention. 
3 See paper by W. H. Garman, entitled, “The egg- 
case and larva of Hydrophilus triangularis Say.” 
(Amer. naturalist, Aug. 1881, v. 15, p. 660-663, fig. 1-3.) 
Paris. France, 16 Dec. 1881. 
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