Note 205 — Chapter IX · ARACHNIDA—INTRODUCTION

This and the following Sub-class correspond with Lankester’s Sub-class Euarachnida. The Delobranchiata have gills patent and exposed, and adapted for breathing oxygen dissolved in water. The Embolobranchiata have either the gill-books (now termed lung-books) sunk into their body, or the gill-books are wholly or partially replaced by tracheae. In either case the members of this Sub-class breathe atmospheric oxygen.