142 
Prof. Miall and Mr. N. Walker on the 
aquatic. It breathes air, and often creeps out of the 
water altogether. This is rather troublesome to anyone 
who keeps the larv^ in captivity, for they stray from 
their saucers, if precautions are not taken. Flies 
reared in the laboratory of the Yorkshire College were 
sent to Mr. R. H. Meade, of Bradford, who has kindly 
examined and named them. 
Description op the Larva. 
The body is 8 mm. long, and consists of a head, 
followed by eleven segments. Transverse constrictions 
subdivide the segments. Each thoracic segment con- 
sists of two annuli, while most of the abdominal seg- 
ments consist of three. Traces of a third annulus can 
be seen in the thoracic segments, but the constriction 
is not complete. The first abdominal segment has 
only two annuli, and the eighth is apparently undi- 
vided. It is possible that this eighth and last 
abdominal segment consists of an eighth and ninth 
fused together, but there is no proof that this is the 
case. 
The body is densely covered with chitinous tubercles, 
for the most part very minute. These appear under the 
microscope like nails imbedded in the flexible skin. 
They take various shapes according to their position, 
some being long and slender, others stumpy. A pro- 
minent rim unites them more firmly to the skin. This 
external armour is a great obstacle to anatomical exami- 
nation, and no doubt protects the living animal either 
from the attacks of its enemies or from abrasion. 
Inhabiting stony channels and subject to a rush of 
water bearing silt and gravel with it, the larva may 
well stand in need of a defensive armour. 
The more exposed parts of each annulus are protected 
by chitinous shields in addition to the tubercles, which 
here become less numerous. There is a narrow, trans- 
versely set dorsal shield to each annulus. Along the 
middle line of each shield is a narrow patch of tubercles, 
while its lateral extremities bear processes like para- 
podia, ending in one, two, or three long and stout setae. 
The dorsal shields of the first three annuli are divided 
along the middle line. The use of this provision appears 
at the time of pupation, when the integument splits 
along the very same annuli to allow of the escape of the 
