THE EVOLUTION OF THE HEAD REGION IN LOWER ARTHROPODS AND ITS BEARING UPON THE ORIGIN AND RELATIONSHIPS OF THE ARTHROPODAN GROUPS

Abstract

As is indicated by the numbering of the figures in the accompanying plates, the following discussion of the head capsule of lower Arthropods is a continuation of the discussion of the head capsule of higher Arthropods given in a previous paper (Canadian Entomologist, LX. 1928, p. 129). The figures were numbered consecutively throughout all of the plates which were originally intended for inclusion in a single paper, and the original numbering has been retained in the accompanying plates (despite the fact that limitation of space necessitated dividing the original discussion into two parts) because reference was made to certain of the accompanying figures in the previous paper, and it would create confusion to later change the numbers which had been referred to in a previous paper. On this account, the accompanying plates begin with “Fig. 55.” instead of “Fig. I.”