June, i9-'i.l CraMPTOX : EvOLL'TIOX OF THK. AXTHRUPOUA. 



75 



upon the interpretation of tiie area labeled " nio " in Fig. 2^, as the 

 molar area alone, and I have only i^rovisionally interpreted it as such 

 until I have been able to study other related forms in order to 

 definitely determine the i)oint in question. 



Textfigitri 4. Mandible of Mysis. Te.xtfigiirc 5. Mandible of Afseudcs. 

 Textfitrure 6. Mandible of Macliilis. 



A stage beyond that represented in textfigure 3 is illustrated by 

 Mysis, shown in textfigure 4 (compare also I-"ig. 7 of Plate \I). 

 Tltysaiiof^oda or Eiiphausia would doubtless have proven to be much 

 better in many respects than Mysis for such a phylogenetic study, but 

 one must perforce do the best he can with such material as he is 

 able to procure, and the Crustacea in question are among the number 

 of certain interesting and much-needed specimens which I have as 

 yet been unable to procure for study I M ysis, however, serves the 

 purpose fairly well, and by comparing textfigure 4 of Mysis. witli 

 textfigure 3 of Xcbalia, the following changes may be noted as we 

 pass from the more primitive types of Crustacea to those which ap- 

 proach more closely to the types ancestral to the higher Crustacea, 

 insects and "' myriopods." The endopodite "en" (or mandibular 

 palpus) becomes proportionately smaller as the basal segment of the 

 mandibular appendage grows larger and becomes better adapted for 

 chewing purposes. It is possible that the endopodite " i'» " of 

 Xcbiih'a (textfigure 3. or Fig. 10 of Plate \T) might be of .some use 

 in swimming. At any rate, it can beat outward with a movement 

 which it would be apparently imi)ossible for the endopodite " en " 



