REPORT ON THE PHYLLOCARIDA. 31 



Homology of the Carax^ace. — As above mentioned, the carapace in Nebalia has been 

 adduced as a character showing the affinity of this genus to the Podophthahnia, and 

 especially the Schizopoda. On closer examination we shall, however, find that accordiuo- 

 to this character it might with quite as good reason be classed among the Phyllopoda ; 

 for both the finer structure of the carapace and the manner in which it is connected with 

 the body are rather more in accordance with the latter Crustacea than with the Podoph- 

 thalmia. Moreover, the presence of a well-developed adductor muscle, never found in 

 any Podophthalmia, gives the carapace in the Nebaliida3 a very marked phyllopodous 

 character. As to form and relation to the body, it exhibits, as it were, an intermediate 

 condition between the carapace in Apus and the bivalved shell in Limnadia. The jointed 

 rostral plate is a character neither found in the Podophthalmia nor in the Phyllopoda, 

 whereas a quite similar movable rostral projection is met with in some Copepoda of the 

 Harpactoid group, and in the latter forms, moreover, the lateral parts of the so-called 

 cephalic segment are found to extend more or less down the sides, so as to include between 

 them the bases of the antennae and most of the oral parts, thus assuming the character 

 of a bivalvnlar carapace, though being still connate with the body along the dorsal 

 surface. The greatly developed carapace, by which the Nebaliidffi at first sight seem to 

 be so very sharply distinguished from the Copepoda, may thus be found to have in fact 

 its homologue also in the latter Crustacea. 



Homology of the Eyes. — The eyes form another character wrongly adduced to show 

 the affinity of Nehalia to the Podophthalmia. In reality the eyes in the Nebaliidfe, 

 though properly termed stalked and mobile, differ essentially from those in the Podoph- 

 thalmia by their much simpler structure and by the want of a distinct facetted cornea. 

 On the other hand, they are found to agree, both as to form and structure, very closely 

 with the eyes in a well-known family of the Phyllopoda, the Branchipodidaj. 



Homology of the Antennulie. — These limbs certainly exhibit a structure very different 

 from that met with in other Branchiopoda, but they are also quite dissimilar to the 

 corresponding limbs in the Podophthalmia, diifering essentially as well by the abnormal 

 number of joints in the peduncle, this being in all higher Crustacea invariably but three, 

 as also by the peculiar setose lamella appended to the end of the peduncle. To comjiare 

 this lamella, as proposed by some authors, to the so-called antennal scale belonging to 

 the succeeding pairs of limbs, the antennge, in Decapods and Schizopods, is, in my 

 opinion, cpite unreasonable. Neither can it properly be regarded as homologous with the 

 inner flagellum in these Crustacea or to the accessory flagellum in the Amphipoda, since 

 it is affixed outside the true flagellum, which latter undoubtedly answers to the outer 

 flagellum in other Crustacea, bearing, as it does, the characteristic sensory appendages, 

 generally termed olfactory cilia. Thus the lamella under consideration cannot projDcrly 

 be compared to anything met with in the higher Crustacea, but apparently represents a 

 characteristic feature peculiar to the Nebaliidas. I think we may better understand the 



