PREFACE 
THE Editors feel that they owe an apology and some explanation 
to the readers of 7he Cambridge Natural History for the delay 
which has occurred in the issue of this, the fourth in proper 
order, but the last to appear of the ten volumes which compose 
the work. The delay has been due principally to the untimely 
death of Professor W. F. R. Weldon, who had undertaken to 
write the Section on the Crustacea. The Chapter on the 
Branchiopoda is all he actually left ready for publication, but it 
gives an indication of the thorough way in which he had intended 
to treat his subject. He had, however, superintended the 
preparation of a number of beautiful illustrations, which show 
that he had determined to use, in the main, first-hand knowledge. 
Many of these figures have been incorporated in the article by 
Mr. Geoffrey Smith, to whom the Editors wish to express their 
thanks for taking up, almost at a moment’s notice, the task which 
had dropped from his teacher’s hand. 
A further apology is due to the other contributors to this 
volume. Their contributions have been in type for many years, 
and owing to the inevitable delays indicated above they have been 
called upon to make old articles new, ever an ungrateful labour. 
The appearance of this volume completes the work the Editors 
embarked on some sixteen years ago. It coincides with the 
cessation of an almost daily intercourse since the time when they 
“came up” to Cambridge as freshmen in 1880. 
S. F. HARMER. 
A. E. SHIPLEY. 
March 1909. 
