154 



liaes. They give the surface of the egg sornewhat the appearance 

 of morocco leather. Under cornpression they disappear, and in the 

 later stages of development they are less marked than in the 

 earlier stages. As I ruentioned before, the eggs seem to increase 

 a little in size during development, and this swelling may perhaps 

 be the reason of the disappearance of the ridges. 



The outer raembrane presents a regular destribution of minute 

 punctures. On closer scrutiny these punetures appear as stnall 

 round rings with a minute point in the middle, and in optie 

 section they are seen as shallow deepenings of the surface ending 

 in a fine line running at right angles to the surface and trans- 

 versing the entire thickness of the capsule, that is to say, appearing 

 as a pore-canal. At one point of the egg-surface the punctures of 

 the surface do not appear as rings but as irregular oval forms 

 radially arranged around a centre (Plate VIT, fig. 5). In the centre 

 a round opening is to be seen, the external orifice of the micro- 

 pyle. The capsule is thicker at this point. Everywhere else the 

 arrangement of the small punctures is very regular. 



Such a punctate appearance of the capsule has been described 

 for many eggs, but usually it is not so strongly marked as in 

 Trachinus-eggs. It may here be of some value in distinguishing 

 the earlier stages of development from other pelagic eggs of the 

 same size. 



The yolk is entirely homogeneous, the perivitelline space is narrow. 



The number of eggs produced by one individual at the same 

 time is not very great, but still it is sufficiënt to carry out the 

 artificial fertilisation and to study the development of the eggs 

 until the critical period. 



The first stages of development do not differ from those of 

 other eggs, at least as far as I could see when studying the live 

 eggs. The rate of development is rather rapid, the eggs hatching 

 in about four or five days. 



So in one series (artificial fertilisation on July 29 th 9 a. m.) at 

 about three hours after fertilisation (temperature of the water 16° C.) 

 most eggs were in the four-cell stage. Four hours after fertilisation 



