Rev. T. R. R. Stebbing on Amphipodous Crustaceans. 343 



brushes, were the same ; the walking-legs were the same ; the 

 pleon, with the exception ah'eady mentioned, was the same. 



Of Boeck's three species, only Anonyx ( Orchomene) pinguis 

 is said to have setose branches to the last pair of caudal appen- 

 dages. This species, together with that called minutuSj is said 

 to have red eyes, while to setyatus black ones are assigned. 

 Messrs. Bate and West wood, however, say of their Anonyx 

 Edwardsi, which is the Orchomene serrata of Boeck, that the 

 eyes are red in the young, but become black in the adult 

 animal. No doubt the colour is variable. Certainly in Am- 

 phithoe littorina the eyes, which these authors state to be black, 

 are not unfrequently red. 



As to the upper antennae, Boeck says of the first joint of the 

 peduncle that it is in 0. pinguis very thick, in 0. serrata pretty 

 long, in 0. minuta short and thick | while he compares the 

 length of the first joint of the ilagellum respectively to that of 

 five or six, of two or three, and of three of the following arti- 

 culations united. The other distinctions are of a similar cha- 

 racter, relating almost exclusively to differences of dimensions. 

 These cannot be relied on in comparing animals in other respects 

 nearly alike, for the simjjle reason that in the growth of all 

 living creatures the proportions of various parts are liable to 

 change, and are besides very frequently different in the two 

 sexes. Thus the head of a tall man may be one eighth of his 

 whole height, but the head of a child will be a much larger 

 fraction of its complete stature. 



The contention here advanced, that the long lower antennas 

 and setose final pleopoda are in some cases characters of 

 the male sex, is supported by the opinion which Messrs. Bate 

 and Westwood express to the same effect in regard to a spe- 

 cimen oi Phoxus pluviosus (Brit. Sess. Crust, vol. ii. p. 527). 

 It may also be considered certain that where animals are only 

 to be distinguished by the length of the lower antennas, those 

 with the shorter antennas are the females or juniors, antenna 

 of an intermediate length, without calceolse, indicating a male 

 not full-grown. Such a specimen has presented itself among 

 others of Anonyx serratus. 



If this rule be accepted, and the uncertainty of specific di- 

 stinctions grounded on proportion of parts or setose adornment 

 be recognized, the opinion here advocated (that i\\Q, Anonyx ox 

 Orchomene variously called ^n'/j^'^ 25, serratus, ov nmiutus is the 

 one species Anonyx serratus) will have a good chance of pre- 

 vailing. But the same data seem capable of further exten- 

 sion. Already Lilljeborg has shown that the Anonyx ampulla 

 and A. longipes of the ' British Sessile-eyed Crustacea ' are 

 both of them A. longipes, the so-called A. ampulla (which has 



