ON THE MICROSCOPIC ANATOMY OP AN INSECT LARVA. 607 
body^ tbroiigb tbe whole of the third and a part of the fourth 
segments_, is a very narrow colourless oesophagus (fig. m) ; 
its delicate walls and small calibre form a striking contrast 
to the large pharynx and stomach on either side. The stomach 
commences in the second half of the fourth segment_, and 
continues to the end of the eighth. Its walls are very 
muscular^ and are composed of three tunics and external 
serous or structureless membrane^ a middle muscular and an 
internal glandular layer. The glandular portion is by far the 
most highly developed^ and the cells of which it is composed^ 
containing very distinct nuclep and of a dull yellow colour^ are 
very easily seen. The glandular layer most probably secretes 
some fluid to aid the digestion of animal matters^ similar to 
the gastric juice of higher animals. At the point where the 
stomach terminates^ at the beginning of the ninth segment^ 
five different continuations of it are given oflP (fig. 8). The 
central one is the intestine_, the other four being glandular 
caecal appendages. Two of these caeca terminate in the tenth 
segment_, and two are continued into the last^ or eleventh. 
Leydig in his paper only mentions two of these bodies, and 
does not figure them at all. They are tubular in form, their 
walls being very thick, and containing very numerous cells 
of large size and granular matter. What their function may 
be is not easy to conjecture.* The intestine through the ninth 
segment is of very small dimensions, but highly elastic, and 
resembles the oesophagus ; in the tenth segment it expands 
into a pear-shaped organ, which has very muscular walls, and 
seems to form a sort of reservoir for the faecal matters. The 
pear-shaped sac extends only through the tenth segment ; in 
the eleventh it is succeeded by a straight rectum, which com- 
municates with the exterior by an aperture in the centre of 
the four terminal plates, of which we have already spoken. 
The remarkable form of alimentary canal just described is 
adapted to the requirements of a carnivorous animal. The 
Corethra larva is a great devourer of entomostraca, particularly 
the Bajphnia pulex, which it demolishes with astonishing 
rapidity. Its predatory habits were noted by Mr. Brightwell, 
of Norwich, in the Zoological Journal of 1833, and a very 
bad figure of the larva given. Reaumur also gives a poor 
sketch of the little creature in his work on insects ; but neither 
the one nor the other gives any idea of the details of its form or 
structure. 
Organs of respiration . — When the Corethra larva is swim- 
ming about in the vfater, besides the two black eye-spots 
These glandular caeca seem very similar to the pyriform bodies described 
by Mr. McAlister from the nematoid parasite of Testudo graeca (A. N. H.. 
July, 1865). 
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