EEPORT ON THE PHYLLOCAEIDxV. 31 



Homology of the Ccwapace. — As above mentioned, tlie carapace in Nehalia has been 

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

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

 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 Nebaliidaj 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 antennas and most of the oral parts, thus assuming the character 

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

 surface. The greatly developed carapace, by which the Nebaliidse 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 Nebaliida?, 

 though properly termed stalked and mobile, difier 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 arc found to agree, both as to form and structure, very closely 

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



Homology of the Antemmlce. — These limbs certainly exhibit a structure very difi"erent 

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

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

 number of joints in the peduncle, this being in all higher Crustacea invariabl}' but three, 

 as also by the peculiar setose lamella appended to the end of the peduncle. 'i"o cumpare 

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

 the succeeding pairs of limbs, the antenua3, in Decapods and Schizopods, is, in my 

 opinion, quite unreasonable. Neither can it properly be regarded as homologous vnXh. 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 properly 

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

 characteristic feature peculiar to the Nebaliida;. I tliink we may better understand the 



