Note 147 — Chapter VIII
Reading edition
The oldest Tracheate actually known to bear spiracles is the Silurian Scorpion of Gothland and Scotland (Scudder, in Zittel’s Palæontologie, p. 738). We need not say that this is very far removed from the primitive Tracheate which morphological theory requires. The existing Peripatus makes a nearer approach to the ideal ancestor of all Tracheates, if we suppose that all Tracheates had a common ancestor of any kind, which is not as yet beyond doubt.