SEGMENTATION OF THE HEAD OF DIPLOPODA. 609 



monoprosthomera) far away from the Chilopods, Hexapods, 

 and Crustacea (Pantagnatha triprostliomera), in his 

 recent classification of the Arthropoda. 



The latest writer on the subject, Carpenter (1905), has 

 found what he interprets as two pairs of maxillfe in the 

 gnathochilariura of Polyxenus (adult). He also expresses 

 the confident anticipation that the median parts of the 

 gnathochilarium will be found to belong to the post-maxillary 

 segment. This would imply the existence of three maxillary 

 segments in Diplopoda. 



Among the recent writings on the segmentation of the 

 Diplopod head it seems only necessary to mention those of 

 Professor Lankester (1903), Heymons (1901), and Cai-penter 

 (1905). 



Professor Lankester, considering the head as monopros- 

 thoraerous, places the Diplopoda far away from the Chilopoda, 

 Hexapoda, and Crustacea. 



Heymons considers the differences between the Diplopod 

 head and those of the other groups to be not radical, for he 

 admits the existence of a tritocerebrum in the adult Diplopod 

 (St. Remy, 1890), and also because he would include the 

 post-maxillary segment in the head, considering it as a 

 rudimentary maxillary segment, thus giving the head six 

 segments as in the other tracheates. 



Carpenter too is unable to consider the Diplopod head as 

 monoprosthomerous, partly because he believes in the 

 existence of an ocular segment, and also because he is in 

 hopes of a tritocerebral segment being demonstrated in an 

 embryo millipede. 



Methods. 



The eggs were fixed for the most part in Perenyi's fluid, 

 but for some corrosive sublimate and acetic acid were used. 

 Pei-enyi is excellent for hardening the yolk, but the second 

 method gives far better histological results. 



I can fully endorse Folsom's (1900) statement that the 



