1909.] NATURAL SCIENCES OP PHILADELPHIA. 9 



similar mode of life frequently leads to a remarkable convergence in 

 structure, which would, however, have no value in a genetic homolo- 

 gization. Furthermore, it must be borne in mind that insects are not 

 descended from myriopods, but that recent Myriopoda, Crustacea, 

 Insecta, etc., are groups of equal rank; and modifications in any direc- 

 tion may occur in each of the groups, quite independently of what 

 occurs in any of the others. 



Patten's argument, that the presence of two cross commissures in 

 each neuromere is indicative of its double nature, loses its force when 

 we consider that in many insects the last abdominal ganglion — which 

 is regarded as the fusion product of a number of neuromeres — likewise 

 contains but two cross commissures; whereas, if Patten's argument 

 were correct, there should be as many commissures present as there are 

 neuromeres entering into its composition. With regard to the bifur- 

 cated maxillae of insects, it would appear far more reasonable to explain 

 this condition as a secondary development, rather than the persistence 

 of a primitive condition in such highly specialized appendages as the 

 mouth parts; and Patten's other argument, that insect abnormalities 

 with double pairs of legs are of frequent occurrence, has no weight 

 when one considers the fact that there are likewise many vertebrate 

 monsters with double appendages — yet no one considers this as a 

 reversion to the primitive condition. 



With regard to Kolbe's, '93, conclusions based upon the thorax of 

 the larva of Lampyris, etc., it must be remembered that the larval 

 form by no means represents the most primitive condition, but is 

 rather an adaptation to its mode of life, as is so well shown in the 

 hypermetamorphosis of Sitaris humeralis. Again, in certain lepidop- 

 teran larvae — Sphinx for example — it is very easy to observe a marked 

 tendency toward the formation of intrasegmental rings ; and this sug- 

 gests that the extra constrictions in the soft larval bodies of Lampyris, 

 Rhaphidia, etc., are probably some such superficial modifications, 

 especially since no indications of any subdivision is indicated in such 

 important segmental structures as the ganglia, tracheae, etc. 



Banks', '93, theory, that the meso- and metathoracic styli of Machilis 

 are rudimentary legs, has no support either from an embryological 

 or a structural point of view, and he seems to have been unaware of 

 Haase's, '89, far more probable explanation of these structures as 

 modified setae. Furthermore, Borner, '03, and Henneguy, '04, recently 

 homologize these organs with the exopodite of the Crustacea, while 

 Verhoeff, '03-'04, following Haase, '89, compares them to the coxal 

 organs of Myriopoda. 



