486 Mr. C. Spence Bate on the 



the period of coition, and that it assists by compressing the 

 male organ against the vulva of the female. I am inclined 

 to think, from the variation of this organ in other families, that 

 there may be a tendency to vary in size the nearer or the 

 more distant may be the rutting-season. It varies somewhat 

 in form with the species. 



Willemoesia leptodactyla. C, posterior extremity of carapace ; o, fifth 

 pereiopod, witli tlie orifice of the male organ in the basal joint ; 

 p, first pleopod. 



The second set of questions that the Eev. A. M. Norman 

 proposes relate to the eyes. " Eyes," he says, '' are things to 

 see with." True ; but he must admit that they are not always 

 available for this purpose. Then the Rev. A. M. Norman 

 says, " Has Polyclieles such organs?" Most decidedly it has; 

 and I gave a distinct figure of one in the October number of 

 the ' Annals.' But why did not the Rev. A. M, Norman 

 examine the specimens in his possession ? he would not then 

 have had to write, " it were to be wished that Mr. Bate 

 had lettered the figures of the plate to have made them more 

 clear." Had I thought there would have been any difficulty 

 in understanding them I would ; but I felt that I was writing 

 for advanced carcinologists, and therefore thought that the 

 references would be unnecessary*. 



Most certainly the eye I described is not on " the base of the 

 peduncle of the inner antennse," which, from its situation, can- 

 not be the homologue of the true eye. That which I describe 

 as being the eye is homologically the same as that found in 

 Astacus, Cancer, &c. 



* I see that, in the plate alluded to, fig. 1° has no reference; it is the 

 fifth pereiopod of Pentacheles gracilis. 



