NO. II LEGS OF PRIMITIVE ARTHROPODS — EWING 3 



primitive groups related to the insects. Nevertheless the trochantero- 

 femoral articulation should be regarded as a " landmark " of great 

 importance in interpreting the segmentation of insect legs. 



The question of the segmentation of the body and the segmenta- 

 tion and musculature of the legs in primitive arthropods has been 

 approached from the standpoint of a taxonomist, using that term in 

 its broadest sense as applying to one who has been interested in classi- 

 fication primarily as bearing on natural relationships and evolution. 



It is lamentable that there is so frequently shown a lack of coopera- 

 tion and helpfulness between the taxonomist and the morphologist. 

 The separation between these two groups of workers has in some 

 instances become so great that not only is there a lack of the proper 

 cooperation in conducting the investigations, but the taxonomist does 

 not even read the literature dealing with the morphology of his own 

 group, and the morphologist seldom consults taxonomic papers, even 

 outstanding monographs. The result is that taxonomy and general 

 entomology have suffered greatly from a multiplicity of terms, from 

 the use of several terms to indicate the same structure, and in con- 

 sequence many have become befogged in regard to obvious facts in 

 evolution and relationships. 



Before passing to the results of this investigation the writer wishes 

 to express his indebtedness to R. E. Snodgrass, whose recent treatise 

 on the " Morphology and Mechanism of the Insect Thorax " (Snod- 

 grass, 1927) has been of great help to him in undertaking this in- 

 vestigation. 



THE PRIMITIVE ARTHROPOD APPENDAGE 



Two questions of importance arise concerning our concept of the 

 primitive type of arthropod limb : Was it a simple, filiform, un- 

 branched structure or was it biramous ; and how many true segments 

 did it contain? There has been a general tendency to look to the 

 Crustacea in searching for the answer to these questions, and doubt- 

 less with much reason, yet the writer is of the opinion that a study 

 of the arachnid limbs is eqvially important if not more so. Probably 

 the Crustacea have been chiefly considered because of their supposed 

 relationship to that very large and very important class, the Insecta, 

 and because of their evident affinity with the much studied, ancient 

 and extinct group, the Trilobita. 



Hansen (1893 & 19^5), in two highly important papers, has led 

 the way in his investigations in regard to the search for the generalized 

 type of appendage for the Crustacea. He pointed out that an addi- 



