Rev. A. M. Norman on Recent Eiyontidae. 181 



at present it appears to me that there is no arrangement so 

 constant as that which I propose." 



The other exceptions occur in Polycheles (as that genus is 

 defined by Bate), in two species out of three of which he has 

 females with styliform last feet. On examining the figure of 

 Polycheles crucifer which accompanies Suhm's paper, it would 

 seem that the inner antenna? are without the scale which is 

 characteristic of Polycheles of Heller, and which I stated in 

 my former notes to be the chief character that seemed to 

 separate Polycheles from the supposed extinct genus Eryon. 

 Can it be that Polycheles, as defined by Bate, with simple last 

 pereiopods in both sexes, has the inner antenna? without a 

 scale, and is in reality Eryon ? It would be of especial interest 

 should it prove so ; but I am not sure that Bate's fig. 6 does 

 not show the antennal scale to the left of the figure ; but in 

 that case it is very remarkable from having a deeply serrated 

 edge. 



It seems necessary that I should add a few words respecting 

 the homologues of the eyes in these Crustacea. Mr. Spence 

 Bate has very kindly sent me a copy of plate xiii., in which 

 he has lettered what he considers to be the eyes in the several 

 figures. They are not the same organs which Heller took to 

 be the rudiments of the eyes ; and I venture to think that 

 Bate is right and Heller wrong in his homology. But that 

 these organs are used for vision I cannot conceive to be pos- 

 sible. It will be found among the stalk-eyed Crustacea that 

 loss of vision and consequent change of function in what would 

 ordinarily be the eye is accompanied by one or other, or by 

 both, of the following modifications : — 1st, that the eyestalk is 

 no longer movable, but becomes firmly fixed in the socket; 2nd, 

 that the eye assumes a difference of form, and is either (a) nar- 

 rower and pointed, instead of club-shaped at the extremity, and 

 so employed (in some instances at any rate) as an organ of 

 offence, as in Ethusa granulata, Norman, or Cambarus pellu- 

 cidus, Tellkampf, or (b), on the other hand, becomes expanded 

 and flattened into a plate, examples of which may be found 

 in the genera Pseudomma, G. O. JSars, Amblyopsis, G. 0. Sars, 

 and Petalophthalmus, Suhm. 



Now, in the Crustacea which we arc considering, Mr. 

 Bate says, the " eyes " are " immovably lodged," and " the 

 peduncle throughout the group is reduced to a minimum 

 and fixed as a rigid part of the dermal structure;" and with 

 respect to form in Willemoesia leptodaclyta they would seem, 

 from the figure given, to be not unlike those of Calocaris 

 McAndrei, Bell ; while in Pentacheles enthrix and Polycheles 

 a uciferj instead of being club-shaped as in veritable eyes, 



