346 
BRITISH ENTOMOSTRACA. 
♦ 
APPENDIX. 
A. 
CYCLOPS QUADRICORNIS. 
The varieties of this protean species are many, and are 
well worthy of being carefully studied. Since the de- 
scription of this species and its varieties was in the 
hands of the printer, I have been favoured with a letter 
from Dr. Beverley R. Morris, of York, containing sketches 
of the caudal segments of four different varieties obtained 
by him in the neighbourhood of that city. In one, the 
two long middle setae of the tail are plumose to the ex- 
tent of a little more than half their length, while the 
external short ones are not plumose at all. In a second 
variety, the two middle setae are plumose for more than 
two thirds of their length, while the external are plumose 
throughout their whole extent. In a third variety, the 
two middle setae are plumose throughout nearly their 
whole length, and the external entirely so. While in a 
fourth, none of the setae appear plumose in any portion 
of their extent. “ These setae," writes Dr. Morris, " I 
have been very careful to feather accurately. ... I 
have been very careful/' he adds, “ to measure as accu- 
rately as I could, the length, &c. of the different parts, 
and I think they may be depended upon. They were 
also all verified by a friend of mine who is with me ex- 
amining the water of this district." Mr. Halliday also 
informs me that a variety occurs frequently in Ireland in 
which the tail setae are not plumose. 
