264 MR. F, BALFOUR-BROWNE ON THE [ Mar. 2, 
appeared below the first at the same distance from the external 
edge of the palp and much nearer the base. 
The lamelle show no change in shape, but the two lateral ones 
now possess two tracheal tubes, the main branch as its enters the 
base having given off a smaller branch which runs up the lamelle 
parallel with the main one. 
In some specimens at this stage circulation of the blood is 
visible in the basal segments of the third pair of legs, but, as a 
rule, there appeared to be no difference in this respect between 
this stage and the previous one. 
Stage 3. 
The antenne now consist of 5 segments, the third from the 
base having divided, cutting off about one-third of its length at the 
distal end to produce the new segment. 
No change takes place in the labial palpi, but one pair of long 
stiff hairs has appeared on the upper surface of the labium itself. 
These hairs are situated nearer the anterior than the posterior 
end and are on each side of the median line fairly wide apart. 
They are directed forwards and, when the labium is at rest below 
the head, are immediately behind the mouth of the nymph. 
The lamellae are slightly wider vertically than before, but 1¢ will 
be necessary to deal with their development separately, as their 
changes apparently correspond with the rate of growth of the 
nymph rather than with the stage in its life-history. 
At this stage there seems to be usually, if not always, cireu- 
lation of the blood in the bases of the legs, but there is still none 
in the antenne or in the lamelie. J am not certain as to when 
circulation begins in these latter organs, but it appears to be 
established about the 6th or 7th stage, if not earlier. One inter- 
esting point concerning it is that it is apparently intermittent, as 
there are times when it is impossible to see any corpuscles moving, 
while at other times the flow is distinct and rapid. The circulation 
in these organs seems to be confined to the region round the main 
tracheal trunks, there being in each lamella a blood-space above 
and below these trachee. The direction of the flow in these blood- 
spaces seems to be reversible, as at times the blood may be seen 
flowing outwards above the trachea and inwards below, while at 
other times the opposite is the case. The circulation in the 
middle lamella also is sometimes the opposite of what it 1s in the 
lateral ones. At times the corpuscles oscillate backwards and 
forwards on both sides of the tracheal trunks. I shall have more 
to say concerning the lamelle when I come to discuss the moults. 
In one individual examined at this stage there were three 
Malphigian tubules. 
Stage 4. 
At the third moult no increase takes place in the number of 
