NORTH SEA INVESTIGATIONS. 33 



On April 26th I examined a number of Trigla giirnardus. I did not 

 note the sizes of these, but all were mature, and in most of them there 

 were some ripe eggs. In each ovary there was every stage of develop- 

 ment, from the transparent egg with a few globules to the large also 

 transparent ripe egg, with its large single copper-coloured oil globules. 

 As in the turbot, what may be called the second stage consisted in the 

 formation of a dark inner zone round the germinal vesicle, with 

 scattered globules in 'the outer region. In the next stage the egg is full 

 of yolk, no clear protoplasm is visible, but there is a marked con- 

 trast between the dark inner zone and the light outer. In the 

 fourth stage the contrast is less marked : the dark inner zone appears to 

 consist of very minute globules of oil, and at this stage they run 

 together and form large globules, in consequence of which the inner 

 zone becomes more translucent. In the fifth stage the coalescence 

 of the inner globules and of the outer into larger and larger drops can 

 easily be seen, and it is perfectly obvious that the inner drops form the 

 oil globule of the ripe egg. Thus the oil globule originates in the 

 central part of the egg, and only rises to the surface when the 

 whole yolk becomes a continuous liquid. 



These facts considerably modify the criticism I have given in vol. 

 iii. p. 2G3, of Scharff's account of the development of the egg. I 

 have not his paper here to refer to, but he worked with the eggs of 

 Trigla gitrnardus, and described the division of the protoplasm of 

 the egg into two layers. In the eggs of plaice and flounder I could 

 only find an outer yolk layer and an inner without yolk. I have now 

 shown that there are at any rate two types in the development of yolk 

 in the eggs, one characterising the eggs without oil globules, the 

 other those that possess the latter. In the ovaries of fish whose 

 eggs possess oil globules, the presence of minute scattered globules, in 

 otherwise protoplasmic eggs, does not imply the " active " condition of 

 the ovary — does not, that is to say, prove that the maturation of the 

 ovary for the next spawning season has commenced. It seems to 

 me quite possible that in these fish also a spent ovary may revert 

 to the condition of the immature, but on this point we have at present 

 little or no evidence. The dark inner zone in the developing eggs 

 above described appears to be due to the presence of exceedingly 

 minute and numerous globules of oily matter, which by their great 

 sub-division and refracting power cause the opacity of that part 

 of the egg. 



V. Two Trips to the Eastern Grounds. 



Ill order to acquaint myself, by personal examination, with the 

 condition of the Eastern Grounds, and the products of the trawling 

 New SERIF..S.— Vol. IV., No. 1. D 



