PREFACE. vii 



It would have been quite impossible for me to have formed an inde- 

 pendent judgment on opposing views in regard to many and those precisely 

 the most important points, if opportunity had not been given me in the 

 kindest manner in very various quarters of studying a number of original 

 specimens and original sections of great value. I here express my hearty 

 thanks to the many persons who have aided me in this manner. I am 

 especially indebted to Dr. W. C. Williamson of Manchester, who gave me 

 facilities for studying the treasures of his collection ; to Drs. W. Carruthers 

 and Woodward of London, to whom I owe my knowledge of the materials 

 in the British Museum, and especially of the collection of sections preserved 

 in that institution and of the treasures bequeathed to it by R. Brown ; to 

 M. Renault of Paris, who assisted me in my examination of the collections 

 in the Paris Museum, and was himself kind enough to explain to me the 

 most important of his preparations ; and to F. Romer of Breslau, who was 

 never weary of supplying me with original specimens from Goppert's collec- 

 tion. Without the friendly help which I received from these labourers in 

 the science, I should never have succeeded in doing any justice to the subject 

 of my book. 



H. GRAF ZU SOLMS-LAUBACH. 



GOTTINGEN, May 27, 1887. 



