VI PREFACE. 



tive groups among Vertebrates, a view wliicli finds 

 ample confirmation in the importance of the results 

 to which Prof. Gegenbaur and his pupils have been 

 led in this branch of their investigations. 



Though I trust that the necessary references to 

 previous contributions in the same department of en- 

 quiry have not been omitted, the * literature of the 

 subject' will nevertheless be found to occupy a far 

 smaller share of space than is usual in works of a similar 

 character. This is an intentional protest on my part 

 against, what appears to me, the unreasonable amount 

 of space so frequently occupied in this way. The pages 

 devoted to the ^ previous literature ' only weary the 

 reader, who is not wise enough to skip them, and 

 involve a great and useless expenditure of time on 

 the part of any writer, who is capable of something 

 better than the compilation of abstracts. 



In conclusion, my best thanksare due to DrsDohrn 

 and Eisig for the uniformly kind manner in which they 

 have forwarded my researches both at the Zoological 

 Station in Naples, and after my return to England; 

 and also to Mr Henry Lee and to the Manager and 

 Directors of the Brighton Aquarium, who have 

 always been ready to respond to my numerous de- 

 mands on their liberality. 



To my friend and former teacher Dr Michael 

 Foster I tender my sincerest thanks for the never- 

 failing advice and assistance which he has given 

 throu<2:hout the whole course of the work. 



