EEPOUT ON THE PHYLLOCAKIDA. 37 



over, in all essential points rather well with that found in Nehalia} The apparent 

 agreement with the Schizopoda in the mode in which the ova and embryos are borne in 

 Nehalia during their development, is considerably lessened by the cii-cumstance that 

 there is in the latter form no trace of any true incubatory pouch, the ova being simply 

 received within the valves of the carapace and kept in place by the aid of the branchial 

 legs. 



Concluding Remarks on the Phylogeny of the Nebaliidie. — Owing to the suggestion 

 made by most naturalists, that Nehalia forms a direct transition between the Phyllopoda 

 and Podophthalmia, it has generally been supposed that the Nebaliidse have descended 

 from the Phyllopoda, and that, on the other hand, all the Podophthalmia should be 

 regarded as descendants from Nehcdia-Yiko. ancestors. In his interesting treatise on the 

 phylogenetic relationship of the Malacostraca, Dr. Boas has sought to strengthen the 

 latter supposition by instituting a close comparison of the limbs in Nehalia with those 

 in the Malacostraca, and has thereby been led to the result, that the connecting link 

 between Nehalia and the great bulk of the Podophthalmia is represented by the 

 Euphausiidse, from which again all the other forms of that division are supposed to have 

 descended. It would seem that the chief reason that has led Dr. Boas to this view as 

 to the supposed close relationship between Nehalia and the Euphausiid^, is the apparent 

 agreement in the number of segments composing the anterior division of the body 

 (cephalothorax), and the uniformity in structure of the eight pairs of limbs succeeding 

 the oral parts in 1:)0th. For in all other points the difference is in reality so very great, 

 as in most cases only to admit of the statement of a very general homolog}^ such as 

 could also be made by comparing almost any forms of Crustacea. It has been stated 

 above that the resemblance of the branchial legs to the legs in the Euphausiidaj is in the 

 genus Patxinehalia considerably more pronounced than in Nehalia. But notwithstanding 

 this agreement, I still believe that there is no true relationship between the Nebaliidse 

 and the Euphausiidse, and tliat the above mentioned apparent conformity in the con- 

 struction of some of the limbs in both is merely accidental, a view that seems also to be 

 confirmed by the fact that in an otherwise closely related genus, Nehaliojjsis, these 

 limbs exhibit a form showing no similarity whatever to the corresponding limbs in the 

 Euphausiidse. If any true consanguinity had existed between the Nebahidaj and the 

 Euphausiida3, the agreement between the two would certainly not be restricted to the 

 above named limbs, but might have been traced also in the rest of the organisation. But 

 this is by no means the case. On the contrary, it may easily be found on closer com- 

 parison, that the Eu])hausiid?e in so far diS'er from the NcbaliidiB even considerably 

 more than is the case with a great number of other ]\Ialaeostraca. 



As to my own view on the probable phylogenetical relation of the Nebaliidse to other 



1 On Cj-clestheria hislopi (Baird), a Now Generic Type of Bivalved Phyllopoda, Forhandl. Vidend: SeUk. Chriil., 

 1887 (to be shortly published). 



