436 OJf ILYOPSYLLUS COKIACEUS AJs'D OTHER CRUSTACEA 



microscopic powers. Between the bases of the fourth pair of feet 

 in the male is a complex lobose organ very similar in general 

 aspect to the copulating apparatus of some Ostracoda (figs. 1 2, 1 3), 

 The spermatophores (fig. 14) are very large in proportion to the 

 size of the animal extending when in situ over nearly one-third 

 of the length of the body. Length -55 mm. 



Hah. — On the surface of mud near high-water mark on the 

 margin of the Eiver Aln. 



The structure figured and described in the Monograph of 

 British Copepoda, as a fifth pair of feet seems to be only a part 

 of tho peculiar organ found at the basis of the fourth pair in the 

 male but non-existent in the female. The situation of the organ 

 would rather lead to the supposition that it may be in some way 

 connected with the reproductive function, but of this I can say 

 nothing certainly. 



The movements of the animal in a living condition are very 

 interesting. I was unable with the imperfect appliances avail- 

 able at Alnmouth, to isolate a specimen under the microscope, 

 but with a hand-lens its habits could be fairly well watched, 

 the brilliant colour of the animal making it conspicuous. 

 So far as I have seen it never attempts to swim, but glides 

 very actively and with a sort of serpentine or eel-like motion 

 among the particles of mud or debris. How the motion is 

 produced I could not ascertain, but my impression is that it is 

 by the action of the tail rather than the feet,— a motion rather 

 of the ''pulsellum" than the "tractellum" kind. The flexible 

 abdomen and long tail, with the massive, immobile character of 

 the anterior part of the body seem to support this view. 



The genus jihacola proposed by C. L. Edwards {loc. cit.) is 

 undoubtedly identical with Ilyopsylhis, the latter name having 

 the claim of priority. Abacola holothurics, however, appears 

 to be parasitic either in or on a sea-cucumber, and is probably 

 distinct from the British species. 



The mouth organs are totally ditferent from those of any other 

 Copepoda known to me. The almost obsolete mandibles, and the 

 reduction of all the other mouth apparatus — maxillae and maxil- 

 lipeds— to a few very minute filaments or setfe, preclude its 



