PREFACE. 207 



blast, the notochord, the limbs, the heart, the venous system, 

 and the excretory organs, are not unworthy of the attention of 

 Morphologists. 



The masterly manner in which the systematic position of 

 Elasmobranchs is discussed by Professor Gegenbaur, in the 

 introduction to his Monograph on the Cranial Skeleton of the 

 group, relieves me from the necessity of entering upon this 

 complicated question. It is sufficient for my purpose that the 

 Elasmobranch Fishes be regarded as forming one of the most 

 primitive groups among Vertebrates, a view which 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 enquiry 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 expen- 

 diture of time on the part of any writer, who is capable of some- 

 thing better than the compilation of abstracts. 



In conclusion, my best thanks are due to Drs Dohrn and 

 Eisig for the uniformly kind manner in which they have for- 

 warded 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 neverfailing advice and 

 assistance which he has given throughout the whole course of 

 the work. 



