470 Prof. K. Grobben on the Oeneahgy and 



In a similar manner Balfour * has already divided the 

 Crustacea into a number of groups and has distinguislicd the 

 following sections as of equal value: — T. Branchiopoda ; 

 II. Malacostraca ; III. Copepoda; IV. Cirripedia; V. Ostra- 

 coda. Although the guiding points of view of the descent 

 appear similarly decisive in Balfour's case also for the foun- 

 dation of these groups, they differ from mine in so far as a 

 tracing-back of these groups to the three Phyllopod types is 

 not considered. 



"With reference to the subdivision of the Malacostraca, T 

 •would remark that the Arthrostraca and Thoracostraca repre- 

 sent the groups distinguished by Claus, with the difference 

 that I set them down as orders. The separation of the 

 Stomatopoda as a special group equivalent to the Arthrostraca 

 and Thoracostraca appears to me to be well-founded, owing 

 to the great difference which these Crustaceans exhibit when 

 contrasted with the other Thoracostraca with which they were 

 united. It corresponds to the theory of their separate origin 

 from Archischizopods, as I have already explained. Claus f 

 interprets the great difference between the Stomatopoda and the 

 rest of the Thoracostraca and Arthrostraca in somewhat diffe- 

 rent fashion, since he even regards the Stomatopoda as having 

 arisen separately from Archimalacostraca. The agreement of 

 the Stomatopoda with the Thoracostraca and Arthrostraca in 

 the formation of the telson and in the number of the abdo- 

 minal segments, as well as the great agreement of the youngest 

 known Ericlit/ioidina-lcivva. with the Schizopods, decides me 

 to combine the Stomatopods as Eumalacostraca with the two 

 groups mentioned, and to derive them all from Archischizo- 

 pods, and, on the other hand, to place the Leptostraca, which, 

 with Claus, we must regard as remnants of Archimalacostraca, 

 in contrast to the Eumalacostraca. By the retention of the 

 branchipodiform furca, the larger number of the abdominal 

 segments, and the peculiar shape of the thoracic feet as well 

 as of the shell, the Leptostraca are proved to be much more 

 primitive than all other Malacostraca. In order to give clear 

 expression to my view as to the affinities of the Stomatopoda, 

 the genealogical tree of the Malacostraca may here be given ; 

 its agreement in other respects with that set up by Claus will 

 appear from a comparison of the two. 



104. 



* Balfour, op. cit. p. 434, note 1. 



t Claus, * Neue i3eitrage zur Morphologie der Crustaceen,' pp. 96 and 



