328 
I^art III, — Ninth Anmial Report 
ordinary character of pelagic ova, with, in addition, a slight sheen like 
those of the plaice, a feature probably due to the peculiar structure of the 
surface and the thickness of the capsule. When closely inspected, the 
zona radiata is minutely wrinkled, the ridges interdigitating with each 
other in a complex manner, somewhat like irregular basket-work (PI. X. 
fig. 1). In those best marked a main series of interlacing ridges, generally 
running obliquely into each other, is evident, the interspaces being 
filled up with subordinate ridges which thus somewhat closely stud the 
entire surface. When compressed and viewed under a high power (PI. X. 
fig. 2), the stratum shows a somewhat irregular reticulation of pale streaks 
on the minutely punctured surface."^ The same appearance is described 
by Mr Holt f in his recent valuable paper. He states : — ' Examination of 
* the zona in the living egg (fig. 21) certainly gives the impression de- 
' scribed by Cunningham, but if it is ruptured and flattened out, it is seen 
* (fig. 20) that the markings are extremely irregular. There are certainly 
' two general systems of parallel lines, but these lines are by no means 
* continuous, frequently ending blindly, converging and diverging or bend- 
* ing abruptly to continue their course at a different level. Seen from 
* above, the markings appear as a line to which the thickly-set punctures 
* of the rest of the zona do not extend. By tracing the lines to a point 
' where the zona is doubled over so as to present an optical section, it is 
* clearly seen that they are not ridges at all, but sharp grooves indenting 
' the surface of the zona from about a quarter to a half of its thickness, 
* according to the size of the lines, which are of varying widths. In some 
* instances the sides of the grooves are very slightly raised above the 
' general surface-level. 'J 
The zona in this species is comparatively thick, and the development of 
the embryo, though visible, is not seen with that perfection of definition 
characteristic of the more transparent forms. During development the 
wrinkled surface somewhat resembles morocco leather. 
9th July. To illustrate the development the first series will be taken 
— viz., those fertilised at 8 p.m. on the 8th July. The details of the 
development of the organs it is unnecessary to give, since they difter 
little from those of other forms fully mentioned in the Researclies. At 
1 P.M. on the 9th they were in the multicelled condition, the blastodisc 
being composed of minute cells. These spheres or cells, on the completion 
of segmentation, were elevated, so that the whole surface was botryoidai. 
In many, moreover, the margin of the periblast is raised into little proto- 
plasmic elevations containing nuclei — these elevations occasionally forming 
more than one row. 
10th July. At 1 P.M. on the 10th, the blastoderm fills the circle 
(looking down on the egg from above). 
11th July, 5 P.M. Embryo fully outlined — with the optic vesicles, 
Kupffer's vesicle, and a considerable number of protovertebrse. Some 
hours previously the neurenteric canal ran right into Kupffer's vesicle. 
12th July. Precursors of pigment-specks in the form of small 
granules have appeared along the trunk, but no pigment is absolutely 
visible either under lens or microscope. Cunningham observes that 
* the first development of pigment appeared as black dots on the sides 
* of the embryo ' on the 4th day. 
13th July. The pale processes of yesterday, on the head, body, 
and tail, are now tinted of a gamboge-yellow by transmittted light. 
* M'Intosh and Prince, pi. i. lig. 18. 
t 'On the Eggs and Larvae of Toleosteans, ' Trans. Roy. Duh. Soc, vol. iv., ser. 
it., p. 453, pis. xlviii. and xlix, 
t Ibid., p. 453, 
