Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. With few exceptions, the figures of the species of the Branchiopoda and Lophyropoda have been drawn from living subjects either by myself or by Mr. Wing, who has devoted much time and labour in illustrating this work. Those of the Caligidae and Lerneadae have been done by Mr. Wing exclusively, and from specimens preserved in spirits, most of which have been kindly placed in my hands for the purpose by W. Thompson.