18 J. T. CUNNINGHAM. 
fig. 23 I have not been able to obtain much more information 
than from living material, and I am inclined to think that, 
while the difficulty of preserving and preparing good sections 
of herring ova may be partly the cause of the obscurity, in 
that species the segmentation cavity is not developed to the 
same extent, nor the invaginated layer so distinctly defined, as 
in pelagic ova. 
Significance of the earlier features of Teleostean 
Development. 
In his ‘‘ Gastraea-theorie ”” Haeckel attempted to explain the 
relation of the process of development in a Teleostean ovum 
studied by himself, to the process of development in a typical 
gastrula (4). The eggs on which his observations were made 
were pelagic and were taken by means of the tow-net, near 
Ajaccio in Corsica; they were ‘64 ‘66 mm. in diameter, 
adhered to one another in small masses, and each possessed a 
single large oil globule at the nutritive pole. Haeckel supposed 
these eggs to belong to the genus Lota or some other genus 
among the Gadide allied to Lota. I do not know if it has 
ever been ascertained to what species the eggs he describes 
actually belong: the eggs of the genus Gadus described in the 
present paper are all destitute of oil globules, but it does not 
necessarily follow that such structures are wanting in the eggs 
of all the Gadide. 
In Haeckel’s account of the development, the existence of 
the layer now known as periblast was denied altogether. He 
declared that by the evidence of his Teleostean eggs the false 
parablast theory of His, and all similar theories, according to 
which cells arose in the yolk and afterwards took part in 
the formation of the embryo independently of the two primary 
germinal layers, were completely refuted. The parablast 
theory of His was certainly not the final explanation of the 
significance of yolk-nuclei, but it is curious that Haeckel 
should have adopted a view concerning the yolk-mass which 
was inconsistent with his fundamental proposition that the 
egg, no matter how much yolk it might contain, was a single 
