DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 687 
the transformed substance of the cortex is difficult, if not impossible, to separate from the 
protoplasm of the germ proper, yet the yolk in the main is neither concerned in the 
cleavage of the germ proper, nor actively contributes to. the increase of the embryonic 
tissues. In the Gadoids and other forms no vitelline circulation is established, and the 
absorption of the yolk is a slow and circuitous process.* 
Oleaginous and other Globules—One of us has already published an account of 
these bodies, which form a striking feature in the yolk of many Teleostean ova 
(No. 125). The following remarks refer mainly to 7. gurnardus, and they still further 
explain certain statements in the paper referred to. 
In the ripe ovum of the gurnard the globule (PI. V. fig. 5, og) is of a dull pinkish 
hue under a lens, while by transmitted light it exhibits a brownish yellow or pale salmon- 
tint. It is enveloped by a protoplasmic pellicle which sometimes appears incomplete, 
and forms an equatorial line, with pale pinkish vesicles studded along its border. 
Unlike those forms in which the globule is imbedded in a definite pocket (e.g., Motella), 
the globule in the gurnard, as also in Cyclopterus and Cottus (Pl. I. figs. 2, 3), is most 
mobile, and can be made to pass under the disc when the latter is uppermost. On 
rolling the egg the globule emerges from beneath the disc, and is liberated with a bound 
at the edge of the rim. Moreover, in passing round it flattens out, and again contracts 
its diameter, or rather resumes its more spherical form. At times the globule appears to 
ascend directly through the yolk, though this may be a deceptive appearance, for 
Ransom found in the very mobile globules of Gastrosteus, that while they passed freely 
through the yolk, they could not be made to go “through its centre to get to the 
uppermost segments when the egg is rolled round ; in doing so the drops often separate 
to unite again” (No. 127, p. 436). Ransom accounted for this by the greater density of the 
central yolk-substance. The passage of the globule under the rim is well seen in the egg 
of the gurnard when the germ has extended as far as the equator. In certain morbid con- 
ditions the exact relations of the globule during its movements can be readily determined. 
Thus the globule is often firmly fixed in the dead egg between the opaque blastoderm and 
the yolk, or the globule is seen at the side, and cannot be made to pass beneath the dise, 
possibly on account of the doubling of the edge of the disc, or because the investment of 
the globule and the periblast have become dense and rigid. During the earlier morbid 
stages, however, the globule is observed to pass beneath the somewhat opaque disc, and in 
certain abnormal cases, from pathological change, the globule rolls external to the dise. 
From the above observations it is evident that Mr CunnincHaw’s view (No. 48, p. 6; 
also Pl. II. fig. 19) that the globule moves in the perivitelline space—that is, between the 
yolk and the zona radiata 
passes between the disc and the yolk, and never passes through the protoplasmic cortex 
of the latter, save in rare morbid examples. In those eggs in which the rim has still a 
short distance to traverse the globule continues freely movable, and its surface next 
the yolk often presents a series of small globules and a single large central one. The 

is not borne out, since in experiments, such as the above, it 
* Vide “Significance of the Yolk in the Eggs of Osseous Fishes,” E. E. Prince, Ann, Nat. Hist., July 1887. 
