DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 781 
the stronger and more robust Teleosteans, which are at a very early stage, often long before 
extrusion from the egg, provided with a complex vitelline circulation. In such forms as 
Salmo (Pl. XXII. figs. 4-9), Anarrhichas (Pl. XX. figs. 2, 4, 5), Gastrosteus, Cottus, 
Liparis (Pl. XV. fig. 2), and Cyclopterus, the blood-corpuscles seem to be mainly 
derived from the nucleated particles into which the surface of the yolk becomes broken 
up, and, as already noted, TrumMAN found in Hsow that hemal channels appeared upon 
the yolk, and corpuscles slowly moved towards the heart before this organ showed any 
motion. No such blood-canals are excavated in the yolk of the pelagic forms here 
treated of, indeed no yolk-circulation ever truly exists in the gurnard, cod, and allied 
forms. Nevertheless, the yolk steadily diminishes, and in embryos, fourteen to twenty 
days after hatching, it forms but a very slight projection, and at the end of the first 
month would appear to be entirely absorbed (compare fig. 5, Pl. XIX. and fig. 1, 
Pl. XVL). The surface of the yolk, however, shows during this time rapid disintegration 
(vide Pl. VII. fig. 9), vesicles, granules, and nucleated particles appear in it (Pl. XI. 
fig. 12), and are especially noticeable around the large oleaginous spheres (PI. XI. 
fig. 13) in those forms, such as the gurnard, ling, and others, in which these striking 
bodies occur. The protoplasmic envelope of the globule in such cases becomes richly 
provided with large nuclei showing one or more nucleoli, and similar bodies occur 
superficially over the yolk. In a young perch, eleven to fourteen days old, LEREBOULLET 
observed, just as we have noticed in the Gadoids and other forms, the dorsal aorta, formed 
by the union of the vessels of the branchial arches, sending a supply to the intestine and 
adjacent viscera, and reaching to the extremity of the tail, while of venous trunks the 
two anterior and two posterior cardinals and the subintestinal vein are common to both. 
In Perea, in addition to the above trunks—developed no doubt in all Teleostean larvee, 
a complex yolk-circulation arises, and is supplied by branches from the posterior cardinals 
and from the subintestinal vein, These branches pass over the yolk as simple undulating 
lacunze formed by the separation of the substance of the yolk-cortex, and meet on the 
ventral side of the yolk in a pair of large veins, which form one large sinus, continuous 
with the sinus venosus in the pericardial chamber. LEREBOULLET says of these vitelline 
vessels, that they do not appear to have proper walls, and form an ill-defined and irregular 
network; but on the third or fourth day after hatching the hamal canals acquire definite 
walls, the network elongates, so that the main trunks show a parallel arrangement (No. 93, 
p- 601). In Perca the development of this circulation over the yolk is much more rapid 
than in Hsox, and LEREBOULLET connects this with the larger perivitelline space in Perca, 
as there is a greater need for respiration; and for this reason, he says, in that species “ the 
capsule is spacious, and holds so large a quantity of water” (No. 93, p. 610). The true 
explanation, however, seems to be that the more complex and rapid the circulation the 
more speedily the bulk of the yolk is reduced, and hence a large perivitelline space is 
produced. It is remarkable, however, that in such forms as the gurnard, rockling, the 
flat fishes, and Gadoids, in which no vitelline circulation ever develops, the yolk should 
still show a very rapid disintegration (compare Pl. XII. figs. 1 and 3, with Pl. X. 
