dA The genus Apus in Baluchistan. [ March, 1905. 
cannot say for certain that this one was not of that kind, but 
from its appearance, this seemed unlikely. On approaching the 
pool I found it swarming with the crustacea of which I here give 
a sketch. There must have been dozens of them, all of about the 
same size. I placed one of them in a bottle of water, but it prob- 
ably got injured while removing it from the pool for it died al- 
most immediately. I tried to preserve it in spirit, but the bottle. 
was accidentally broken and the specimen lost, so that the only guide 
remaining to identify it is the rough sketch that I drew the same 
day that I observed these creatures. 
The sketch is drawn approximately of natural size. It is 
quite diagrammatic, but sufficiently detailed to enable clear identi- 
fication of the object represented. The diagram shows distinctly 
the principal features of Apws, the shield with the main details 
of its ornamentation, the anterior pair of eyes, the anterior legs, 
transformed into long antenniform filaments, the expanded branch- 
ial legs protruding on either side of the carapace, the greatly seg- 
mented abdomen and the caudal appendages. The portion of the 
body extending beyond the shield is proportionately longer than 
in the specimens and figures that have been shown to me by 
Major Alcock and Mr. Annandale. Its relative dimension is pos- 
sibly shghtly exaggerated in my sketch. There is no doubt, how- 
ever, that it really was longer than in the examples that I have 
since seen figured or preserved in spirit, for I was particularly 
struck, at the time, by its shape and size. My sketch shows one 
pair of eyes in the anterior part of the shield. There exists, in 
Apus, a third unpaired eye placed slightly further back than the 
line joining the paired eyes, but it is very small and easily escapes 
detection if one does not know of its existence. The caudal 
appendages are much shorter in my sketch than in the figures and 
specimens which I have seen in Calcutta. Perhaps they had got 
broken in my specimen. 
The presence of so large a number of crustacea in the situa- 
tion where I observed them, appears very puzzling. If the pool 
was the remnant of a larger pond temporarily filled by rain-water, 
one can understand that they should have gradually become 
crowded into a small space as the water receded, but their deve- 
lopment must have been very rapid, for if the pool is not one of 
the perennial ones alluded to, it could scarcely have existed for 
more than two months previous. If the pool is perennial and 
normally of the small size it possessed when I saw it, its crowded . 
population is still difficult to account for.} 
As noticed at a previous meeting by Mr. Annandale, it is prob-- 
able that the reputed absence from this country of many vwell- 
known fresh-water invertebrates is due to our scant knowledge of | 
its fresh-water fauna. 
1 Mr. Annandale has drawn my attention to the account of the genus in 
Bird’s Natural History of the British Hntomostraca, according to which , 
Apus can reach a length of one inch after three weeks development from the . 
egg. It has also been noticed in Europe that this crustacean appears sporadi-_ 
cally and suddenly in an unaccountable manner. 
