PREFACE. 



That many of the results recorded in this volume are, even after 

 the many years which have elapsed since they were brought before the 

 notice of the scientific world, but little known in this country ; that 

 through the kind efforts of Mr. P. L. Sclater, F.R.S., and the willing aid of 

 Dr. W. Peters of Berlin, the originals of Mullers plates were placed at our 

 disposal; and that the Delegates of the Clarendon Press accepted the 

 responsibility of publishing it ; are our justifications for the production of 

 the translation of this valuable monograph. 



A. H. G. 



F. J. B. 



Julij yd, 1878. 



