CHAPTER V. 



GENERAL SKETCH OF MARINE TELEOSTEAN DEVELOPMENT. 



IN a work like the present it is unnecessary even were it 

 practicable to give in detail all the authors who have laboured 

 in the field, or to enter into narrative in regard to the type 

 taken to represent the development of the food-fishes. 



Lists of those who have made advances in the development 

 of these fishes will be found in the various treatises and mono- 

 graphs on the subject. In the list appended to the ResearcJies, 

 by one of us and Professor Prince, no less than 160 authors of 

 importance are cited in 1889, and the list has considerably 

 increased since. 



It will suffice if a brief and somewhat popular resume 

 be given, firstly, of the changes which are externally visible 

 in the egg up to the period of hatching, and secondly, of some 

 of the leading structural changes at various stages, mainly 

 followed out by the systematic study of sections. 



For illustrating the changes undergone by such an egg 

 floating about in the sea, we shall take the translucent pelagic 

 egg of the whiting (Fig. 16) in the month of April, and it may 

 at once be stated that it forms a very good type for almost 

 all the bony fishes. As discharged by the adult on the 

 spawning-grounds the translucent sphere consists externally 

 of a hyaline capsule, which under a high power is observed 

 to be minutely punctured, and under certain conditions has 

 a tendency to break into film-like scales of membrane. 



It really consists, however, of a single layer and is not 

 compound as some authors have supposed. 



At one part of the capsule a minute indentation (micro- 

 pyle) is seen leading to the interior, and this aperture has 



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