There seems to be but little doubt that the Tracheata are descended from a terrestrial Annelidan type related to peripatus.
Segmental organ from the 5th pair of legs of peripatus capensis.
Eye of peripatus capensis, as shewn in a longitudinal horizontal section through the head.
In peripatus we have a strange survivor of these primitive Annelid-Tracheates of many million years ago.
These thickened tracts of ectoderm in peripatus and a few other forms can be clearly seen to surround the blastopore.
In this respect also peripatus shews no signs of a primitive condition of the nervous system.
In peripatus capensis the organ in question can hardly be described as tetrahedral.
A similar groove is found in peripatus, and there forms, as I have found, a large part of the supra-œsophageal ganglia.
A preliminary account of the discoveries as to the embryology of peripatus has already been communicated to the Royal Society.
A left leg of peripatus capensis, viewed from the ventral surface; 30.