98 F. G. HEATHOOTE. 
ventral plates. The anterior parts of the two ventral plates 
are fused so as to form a triangular point. A section through 
the fused part is shown in fig. 1. These plates are the “ lames 
pedigéres”’ of Brandt. Ina former paper on Julus (5) I called 
attention to the fact that the differences between the body-form 
of the early stages and the body-form of the adult were essentially 
due to a diminution of the ventral region and an increase of the 
dorsal to such an extent that the dorsal plate came to form a 
complete ring round the body. I also pointed out that the 
larval condition showed a great resemblance to the earliest 
fossil forms of Myriapoda. Now Polyxenus, in its anatomy, 
resembles the larval rather than the adult Julus. If we com- 
pare a section through one of the segments of Polyxenus with 
a section through a larval Julus, such as is shown in fig. 34 of 
my former (5) paper; and again, with a section through a 
segment of a nearly adult Julus, such as is shown in fig. 2 of 
the same paper, the resemblance to the larval Julus and the 
difference from the adult shown in the well-developed sternal 
region, the widely separated bases of the legs, and the less 
developed dorsal region, is sufficiently striking to render it 
worth while to compare the features of its general anatomy 
with the results obtained by the investigation of the develop- 
ment of Julus. 
Of the appendages, the pair that seems to differ most from 
those of other Chilognaths is that of the second post-oral 
segment, the deutomale; these have been described by Bode 
and Latzel (1. c.). The most noticeable feature about them is 
the possession of two palps on either side, the one short and 
broad, the other long and slender. The four-lobed plate of 
the adult Julus is of course without any vestige of similar 
structures, but the larval form possesses two short, broad pro- 
jections on either side, which seem to me to be rudiments of 
structures similar to those of Polyxenus. . 
The sense-organs described by Bode, and supposed by him 
to be olfactory, may be mentioned here, as their microscopic 
structure has never been investigated. Hach of these organs 
consists of a spine inserted into a structure formed by the 
