622 MARGARET ROBINSON. 



Summary op Results. 



There are, in the embryo of Archispirostreptus, two 

 segments, the possession of which would seem to give 

 the Diplopoda a place in the Arthropod system nearer to the 

 Chilopoda and Hexapoda than that which has of late been 

 assigned to them. 



These additional segments are : 



(1) A tritocerebral segment representing the tritocerebral 

 rudiments found by Wheeler (1893) and others in Hexapoda, 

 and by Hey mens in Scolopendra, and also the tritocerebral 

 segment in Crustacea. 



(2) A pair of maxillae (rudimentary) lying in front of the 

 pair which forms the gnathochilarium in the adult. These 

 are most likely homologous with the first maxillae in Chilo- 

 poda and Crustacea, and with the superlinguas (Folsom) of 

 Hexapoda. 



With regard to the development of the gnathochilarium I 

 have unfortunately not been able to add much to our previous 

 knowledge. But the importance of this matter has now 

 become comparatively small, since the existence of a first 

 pair of maxillae has been demonstrated. 



The evidence that I have is incomplete, but it certainly goes 

 to show that the gnathochilarium is part of the head, being 

 formed by the second pair of maxilte which are the only 

 appendages in it ; and that the post-maxillary segment of 

 Heymons and Silvestri takes no part in the formation of this 

 gnathochilarium, but is purely a body segment. 



3Iay 27tli, 1907. 



References to Literature. 



Carpenter, G. II. — "Notes on the Scgmeiitation and Philogeny of the 

 Arlhropoda, with an Account of the Maxillae in Polyxenus lagurus," 

 'Quart. Journ. Micr. Sci.,' vol. xlix, 1905. 



Folsom, J. W. — "The Development of the Mouth-paits of Anurida niari- 

 tiina," •Bull. Mus. Comp. Zool. Harvard,' vol. xxxvi, No. 5, 1900, 



