82 Journal New York Entomological Society. L^'o'- ^>^ix, 



furnished the key to the interpretation of the parts in insects; and, in 

 fact, it is absohitely essential that anyone who desires to give the 

 correct interpretation to the various structures of insects, and who 

 wishes to determine the phylogenetic origin of insects, should give 

 as much time as he is able to the study of the evolution of the parts 

 in Crustacea, which have departed as little as any known forms from 

 the types of arthropods ancestral to the " Myriopoda " and Insecta. 



Machilis is an insect which is structurally much more primitive 

 than most entomologists realize, and instead of being a degenerate 

 winged insect as Handlirsch would have us believe, I would insist 

 that it is absolutely primitive in most respects, and has departed in 

 fact but little from the condition characteristic of some of the an- 

 cestral insects. It has even preserved certain characters suggestive 

 of affinities with the primitive CoUembola — although its closest affini- 

 ties are with the Lcpisma-Ukc Apterygota, and it furnishes us with 

 a connecting link anatomically annectant between the Crustacea and 

 the Lepisma-Vikt types, as well as with the lowest representatives of 

 the winged insects such as nymphal Ephemerida, etc. In fact, the 

 mandibles of Machilis (and to some extent of certain immature 

 ephemerids also) are more like the mandibles of Crustacea than they 

 are like the mandibles of other insects (as is likewise true of the 

 muscles attached to the mandibles of Machilis) and a study of the 

 anatomical details of Machilis (and of nymphal ephemerids also) is 

 absolutely essential in making an attempt to trace the evolution of 

 the insectan type of arthropod. On this account, I have used Machilis 

 to illustrate the probable mode of origin of one type of insectan 

 mandibles; but it is also necessary in such a study to trace the origin 

 of the type of trophi found in the Dicellura (Japyx, Campodea, etc.) 

 as well, since the dicelluran type is one of the primitive types of 

 insects as well as Machilis; but the Dicellura are of less importance 

 despite their remarkable resemblance to the Symphyla {e.g., Scolo- 

 pcndrclla, etc.) since their line of development, in paralleling that of 

 the Symphyla, leads away from the main path of development fol- 

 lowed by winged insects (as exemplified by immature ephemerids) 

 and higher Crustacea, along a line of specialization having no par- 

 ticular bearing upon the developmental tendencies of insects in gen- 

 eral. Machilis, Lcpisrna, and Nicolctia, on the other hand, exhibit 



