566 The Inter-Relationships of Arthropods. [June, 
The discovery by Moseley of trachez in Peripatus at once 
transferred this form to the tracheate phylum, and much was 
expected from it as throwing light on the origin of the other air- 
breathing arthropods. To the writer it does not appear to have 
any close relationship to any of the other “tracheata,”’ but still 
most of all to the chilognaths. Still it is not proven beyond a 
doubt that it is an arthropod at all. 
The so-called antenne are always pre-oral (as shown by 
Kennel in the embryo and Balfour in the adult), and receive their 
nerve supply from the procephalic lobes in advance of these nerves 
to the eyes; thus allowing one to compare them with the pre- 
oral appendages of worms. The trachez and stigmata are not 
metamerically arranged, the latter opening more or less irregu- 
larly over the surface of the body and legs. The legs themselves 
are not distinctively arthropodous, while the numerous segmental 
organs indicate, as has often been pointed out, a very primitive 
form. Indeed, one has but to imagine a Syllid worm to leave its 
natural element and take to the land, losing the sete of its para- 
podia and developing claws at their extremities, losing its median 
antennz and developing tracheal pits for respiration and salivary 
giands to moisten its food, and Syllis becomes Peripatus. The 
other changes would be few. It would still retain its lateral ten- 
tacles, its segmental organs, its peculiar sympathetic nervous sys- 
tem and many details of its digestive tract. In fact Peripatus, in 
_ the light of recent studies, appears nearer the polychztous anne- 
lids than to any of the arthropods unless possibly the chilognath- 
ous myriapods. 
Recapitulating now the results of this hasty sketch, we arrive 
at the following conclusions: Peripatus has departed the least 
from the ancestral annelidan stock, the hexapods the farthest. 
These then will form the extremes of the series. The Acerata 
and Crustacea should be placed near each other, but which is the 
higher is a question. For instance, in the one only one pair of 
segmental organs remains, and these have lost their external 
ducts, while in the other group two pairs of these organs are 
functional through life. On the other hand, two of the post-oral 
ganglia of the Crustacea have moved to a prestomial position 
and have joined the supra-cesophageal ganglion, while in the 
: ne  Acerata but one ganglion has been completely transferred and 
o this has not yet become wholly united with the ganglion formed 
