28 p. G. HEATHCOTE. 



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 

 pedigeres '^ of Brandt. In a 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 

 diflference 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 difi'er most from 

 those of other Chilognaths is that of the second post-oral 

 segment, the deutomalae ; 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 ol 

 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. Each of these organs 

 consists of a spine inserted into a structure formed by the 



