1092 REPORT—1885. 
tion of the spermatozoa reveals no marked differences, except that of size, the usual 
enlarged head and motile filament being distinguishable in all.’ 
The ova treated of in this paper are extremely buoyant, and float, in the living 
and healthy condition, as minute transparent globes, near the surface of the water. 
Loss of buoyancy and transparency, as Professor McIntosh’s observations! have 
shown, indicate an unhealthy or non-living state. After the germinal vesicle, readily 
seen in immature intra-ovarian eggs, is no longer distinguishable, the ovum consists 
of (a) a central globular deutoplasm, destitute of oil-globules in British Gadoids aud 
flat fishes, but exhibiting in 7. gurnardus a single, pale salmon-coloured oil- 
globule like that of Brosmius americanus, a noteworthy American Gadoid ; (6) a 
cortical protoplasmic film, containing minute vesicles and granules; (¢) a thin 
external hyaline capsule, separated from the vitelline mass by a narrow space, the 
‘breathing chamber’ of Newport. The capsule is tough, structureless, slightly 
resilient, free from punctures or striations, and varies in thickness in different 
species. Thus in P. mands its thickness is ‘0001 in.; P. flesus, 000125 in.; G. 
morrhua, ‘00025 in.; and 7. gurnardus, ‘0005 in. One aperture, the micropyle, 
pierces the capsule, and in the species here treated of, it presents the usual simple 
features, being generally situated, excentrically, in the lowermost (germinal) 
segment of the ovum. After fertilisation, the ovum becomes clearer and more 
tense, and a movement of the superficial protoplasm towards the germinal pole 
commences. The surface of the deutoplasmic globe presents at this time a corru- 
gated appearance, but the areas of transference were less definite than Ryder 
indicates,” The cortical protoplasm collects as a germinal disc or cap, which seg- 
ments in the usual manner and performs a retrogressive movement spreading once 
more over the yelk, and epibolically enveloping it. Irregularity in cleavage is 
common, resulting in asymmetry of the disc. ‘his feature was especially notice- 
able in the two reniform cells of the ovum of 7. gurnardus, after the first cleavage, 
but symmetry was restored when the polycelled stages were reached, In some 
forms the blastodermic scutum presents a more acuminate central promontory than 
in others. It is acute in G. merlangus and S. fario (Oellacher), Jess so in G. 
morrhua and T. vipera (G. Brook), quite obtuse in G. eglefinus, T. gurnardus, P. 
flesus, Motella mustela (Brook), and Perea fluviatilis (Lereboullet). ‘The inwardly- 
directed point of the scutum forms the snout of the embryo, and a thickening 
extends outwards (radially) which indicates the developing trunk, The cephalic 
swelling, the neurochord, the mesoblastic muscular plates, develop in the usual 
way, and between the latter the notochord is pushed up. 
The differentiation of the notochord is coincident in many species with the 
closure of the blastopore, e.g., G. merlangus, G. morrhua, P. flesus, and P. limanda ; 
but in 7. vipera and M. mustela it precedes, while in G. eglefinus and T. gurnardus 
it succeeds the closure by an interval of one or two days. A like variation obtains 
in the time of the appearance of Kupfer’s vesicle. 
Several features were next referred to as probably diagnostic, and therefore 
worthy of note, viz., the formation of a protoplasmic reticulation upon the surface 
of the yelk in P. limanda on the eighth day; the appearance of one or more colour- 
less enucleate stellate structures, on the yelk surface beyond the lateral margin of the 
embryo, in G. merlangus on the seventh day. This latter structure assumes the form 
of a ‘ bone-corpuscle,’ and was observed in no other species studied at St. Andrews. 
T. gurnardus, previous to the act of emergence, exhibits on the yelk-surface many 
minute protoplasmic elevations from which pseudopodial processes protrude, Each 
is isolated and exhibits a nucleus and nucleoli. 
Pioment appears to have a diagnostic value in the case of Teleostean embryos, 
though the study of a very extended series of forms can alone establish the conten- 
tion that it affords a reliable means of identification. Pigment appears earliest in 
P. flesus, and as described by Professor McIntosh,® is ‘of a peculiar pale olive-brown 
(brownish-yellow by transmitted light), whereas in P. limanda it is of a more dis- 
1 Report of H.M.s Trawling Commission, 1884, pp. 31-33. 
2 United States Fish Commissioners’ Report, 1882. ‘Embryography of Osseous 
Fishes,’ Pl. I. figs. 6 and 7. 
8 Second Annual Report Scottish Fishery Board. Appendix F. p. 47. 
