Yll 



limited. The structure of these fishes and their place in the general classification of 

 thtt animal kingdom has been to some extent ascertained, but of their conditions of life, 

 their food, rate of growth, the causes which favour or limit their abundance, we still 

 know very little. It was only in 1864, when Professor Sars identified the floating eggs 

 of the cod, that it was first discovered that the eggs of any marine fish passed through 

 their development while suspended in the surface waters of the sea. The know- 

 ledge of structure and classification is not entirely useless from the practical point 

 of view, for it is absolutely necessary as a basis from which to investigate the different 

 conditions of life of the different species. The species must be considered separately, 

 for their mutual relations are so complicated that it is impossible to deal with, them 

 together. 



The object of the present work is to place side by side the results of a scientific 

 study of the common sole and an account of the present condition of the sole fishery, 

 and then to consider what are the possible practical applications of the former to the 

 purpose of maintaining or increasing the supply of soles available for the market. 



The work was undertaken under instructions from the Council of the Marine 

 Biological Association, and the investigations described were carried out at the 

 Association's Laboratory at Plymouth. Nearly the whole of my time and energy since 

 November, 1888, have been devoted to the subject. The instructions of the Council 







were quite general, but from Professor Lankester I have received much guidance 

 as to the scope of the investigations and the plan of the book. The responsibility, 

 however, for all the views and statements rests entirely upon myself. When studying 

 the taxonomical part of the subject in November, 1889, I visited the British Museum 

 of Natural History, and examined all the type specimens of European species of sole. 

 I have to thank Dr. Giinther for the courtesy and assistance I then received from 

 him. At that time I gathered from conversations with him that he still believed 

 in an English species, Solea aurantiaca, distinct from the Solea lascaris of either Eisso 

 or Bonaparte. I was therefore surprised to see that in a communication to the 

 Zoological Society in January last he abandoned this opinion, and adopted the 

 conclusion of most recent writers on the subject that the English and the Mediter- 

 ranean form belong to the same species. My discussion of the question in the 

 present work was written in November, 1889, immediately after my visit to the 

 national collection. 



I have much pleasure in thanking Mr. Dunn, of Mevagissey, and my friend Eupert 



