104 F. G. HEATHCOTE. 
stink-glands were formed comparatively late in the develop- 
ment as invaginations of the dorsal plate, and I came to the 
conclusion that they were not very deep-seated characters. If 
this is so it is not difficult to understand that they may never have 
been developed in Polyxenus, but that the spines may have been a 
sufficient protection. It is worth noting that the Archipolipoda 
had spines, and not stink-glands. From all these points in the 
anatomy of Polyxenus I am inclined to regard it, not as a 
recently formed link between the Chilopods and Chilognaths, but 
as an animal which has preserved certain traces in its anatomy 
of its descent from a common ancestor of the two classes, 
such ancestor being related to the Archipolipoda. I consider 
it as confirming my view that the Myriapoda are descended 
from a Peripatus-like form, and as opposing their descent from 
Thysanura. I am fully aware that insomuch as I investigated 
Polyxenus with a definite idea, I have probably taken a one- 
sided view of the points I worked at; but I hope that my 
work will induce others to investigate this animal more fully, 
and thus increase our knowledge of the various questions 
suggested by Myriapod anatomy and development. 
My work was entirely carried on in the Cambridge Morpho- 
logical Laboratory. 
LITERATURE. 
1. J. Bopr.— Polyxenus lagurus,” ‘Zeitschr. fir die gesammten 
Naturwissenschaften,’ 1877. 
2. Fapre.— Anatomie des organes reproducteures des Myriapodes,” ‘ Ann. 
des Sci. Nat.,’ 4 sér., 1855. 
3. H. GrenacnEer.— Ueber die Augen einiger Myriapoden,” ‘ Archiv fiir 
mik. Anat.,’ 18. 
4. Latzeut.—‘ Die Myriapoden der oesterreichisch-ungarischen Monarchie,’ 
Wien, 1880. 
5. F. G. Heatucore.—‘ The Post-embryonic Development of Julus ter- 
restris,” ‘Phil. Trans. Roy. Soc.,’ 1888. 
