346 BRITISH ENTOMOSTRACA. 



APPENDIX. 



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, 1 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 tlie 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. . . . T 

 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 occm-s frequently in Ireland in 

 which the tail setae are not plumose. 



