Rymer Jones, on Corethra plumicornis. 101 
These last consist of two pairs of crushers, the maxillae 
and the mandibles, both armed with formidable fangs, while, 
to complete the deadly apparatus, spikes of different shapes 
surround the immediate margin of the mouth. 
The internal digestive organs are not less remarkable than 
the complicated machinery described above. 
The commencement of the alimentary canal presents a 
spacious crop, the walls of which are very strong and mus- 
cular ; to this succeeds a gizzard, armed internally with 
teeth, arranged in densely-crowded phalanx — from this a 
tube of remarkable slenderness and of considerable length 
leads to the true ventri cuius, the walls of which are glandular 
and minutely sacculated. To the pyloric extremity are 
attached four (so called) hepatic vessels, while the intestine 
is simple and slightly dilated towards its extremity. On 
placing one of these larvae between the plates of the com- 
pressor, and pressing it moderately, a very curious phenome- 
non presents itself. The muscular walls of the crop, thrown 
into violent action, tear away the gizzard and its slender 
tubular prolongation, and becoming suddenly everted, pro- 
trude from the mouth, having, in this condition, very much 
the appearance of the unfolded proboscis of an Annelidan ; a 
resemblance much enhanced by the denuded teeth of the 
gizzard, that protrude from the extremity of the everted 
crop, which latter continues for a long while to exhibit peris- 
taltic movements ; while the crushed and mangled bodies of 
the swallowed monoculi, upon which these larvse principally 
subsist, are cast into the surrounding water, and testify to 
the efficiency of the curiously-formed apparatus. 
In these diaphanous larvae, the action of the heart is very 
beautifully exhibited : the contractions of its various cham- 
bers succeed each other consecutively, with an apparent 
energy of purpose that reminds the observer rather of the 
untiring pumping of a steam-engine, than of those rythmical 
undulating movements which we should expect to witness in 
a viscus having walls so thin and transparent, and at the 
same time so isolated. It is therefore by no means surprising 
that the dorsal vessel should be provided with a largely- 
developed system of ganglionic nervous centres, the existence 
and distribution of which are plainly traceable when using 
the higher powers of the microscope. These consist of nume- 
rous minute corpuscles, closely resembling in their appearance 
Paccionean bodies, and are distinctly perceptible in the 
vicinity of each compartment of the dorsal vessel, to which 
they are connected by slender filaments. These minute 
ganglia are usually disposed in groups, varying from three to 
