SEGMENTATION AND PHYLOGENY OF ARTHROPODA. 469 
Notes on the Segmentation and Phylogeny of 
the Arthropoda, with an Account of the 
Maxille in Polyxenus lagurus. 
By 
George H. Carpenter, B.Sc.Lond., M.R.I.A., 
Professor of Zoology in the Royal College of Science, Dublin. 
With Plate 28. 
In the introductory note appended to his article on “The 
Structure and Classification of the Arthropoda” (19), 
Prof. HE. Ray Lankester mentions “two authors who, 
while recently writing general essays” on the same subject, 
unfortunately overlooked his article, with its companion 
article on the Arachnida (20), as originally published in the 
‘Encyclopedia Britannica.’ These authors are the late Pro- 
fessor A. 8. Packard, whose paper (24) was read before the 
American Philosophical Society in April, 1903, and the present 
writer, whose essay (3) was communicated to the Royal Irish 
Academy in the succeeding month. It is a pleasure to 
respond to Prof. Lankester’s courteous invitation to discuss 
further in this Journat the questions raised, in the hght 
of his latest invaluable contributions which, as he hopes, 
will now surely “not fail to come under the notice of 
zoologists.” 
The Unity of the Arthropodan type. 
The two papers published almost simultaneously by Packard 
and myself form a striking object-lesson on the wide diver- 
gence of opinion among students of Arthropod relationships. 
