266 MR. F. BALFOUR-BROWNE ON THE [ Mar. 2, 
on, as Schindler (1878) describes 50 or 60 as being present in the 
imago of Agrion puella. 
Stages 6, 7, 8, and 9. 
The labium in stage 6 usually has 4 hairs on each palp and 
three pairs on the labium. Each new pair of hairs as it appears 
on the labium arises between the original hairs, so that gradually 
the series takes the form of a crescent with the ends curving 
forwards stretched across the labium. In stage 7 the condition of 
the labium is usually the same as in stage 6. 
In stage 8 the labium may be just as in the previous stage, but 
often, perhaps more usually, either a pair of new hairs has appeared 
in the crescent or one hair only has appeared, so that there are 
4 hairs on one side and 3 on the other. I noticed this irregularity 
in a number of cases, and although such uneven developments 
occur in other stages they do not seem to be so common as in this 
one. Occasionally there are 5 hairs on each of the palpi. In 
stage 9 there seem to be, with scarcely any exception, 5 hairs on 
each palp and 4 pairs on the labium. 
Stage 10. 
This may be the final stage in the life of the nymph. The 
antenne, if this is the final stage, will be seen to possess 7 segments, 
the additional one having been produced by the division of the 
6th immediately above the small spur already referred to. Iam 
not certain that this division takes place in all the Agrionide, 
but the statement holds good for Agrion pulchellum and puella,. 
Pyrrhosoma nymphula, and Ischnura elegans. I think that the 
nymph of Lrythromma naias has antenne of only 6 segments in 
its final stage, but I can only find notes as to one specimen of this 
species. Similarly, with regard to Hnallagma cyathigerum, the 
only specimen of which I have kept a record had 6-segmented 
antenne in its final stage. When this is the final stage of the 
nymph, the labial palpi usually possess 6 hairs each, while the 
body of the labium has a crescent of 10 hairs more or less evenly 
spaced and all pointing forwards. In other cases, however, the 
labium may remain as in stage 9 or there may be an intermediate 
condition, 5 hairs on each palp and 5 pairs on the labium itself. 
The blood-circulation in nymphs in the later stages is, in the 
legs, apparently the same as described for stage 4. Bowerbank 
(1833, p. 243) describes the blood as circulating in the leg of 
Agrion “ even to the very extremity of the tarsus, where, as in 
the antenne, the particles of the blood are seen to descend on the 
one side of the leg and turning the extreme point to return up 
the contrary side to the one by which they came down.” Even 
in the full-grown nymph I cannot detect a regular circulation 
beyond the trochanters, where the corpuscles can be distinctly 
seen passing from the anterior to the posterior side and returning 
