694 PROFESSOR W. C. M‘INTOSH AND MR E. E. PRINCE ON 
accomplishes fertilisation.* He, however, states that the extrusion of polar bodies, the 
disappearance of the nuclear spindle, and the aggregation of the germinal area may 
take place independently of impregnation. Kriycstey and Connt describe and figure 
a polar globule in the egg of the cunner apparently after maturation. The globule 
appeared in the centre of the aster, and passed through the micropyle. List recently 
does the same in Crenilabrus pavo, the body being globular at seven minutes and rod- 
like at thirty minutes.t Ryper noted in the ovum of Gadus morrhua a minute 
granular papilla projecting from the early germ, and looked upon this as representing the 
polar cells derived from the germinal vesicle (No. 141, p. 477). In Trigla gurnardus, 
twenty-five minutes after the addition of sperms, a somewhat cylindrical nuclear body 
has been observed in the superficial protoplasm (Pl. I. fig. 17, a). It exhibited very 
slow amceboid movements, and five minutes after it was first noted it had shortened 
and contracted in the mid-portion as if dividing into two—a wide granular border 
extending round it (Pl. L. fig. 17, 6). Three minutes later the two separating parts 
closely approached, and the body became still more contracted and compact—the 
granular margin also becoming less (PI. I. fig. 17, c); but the median cincture was still 
plainly marked ten minutes later (PI. I. fig. 17, d). A side view of a similar structure 
in another ovum exhibited two spherical nuclear bodies enveloped in a vase-shaped mass 
of protoplasm, and from the centre of its wide upper surface radial striations diverged 
(Pl. I. fig. 17, e). No similar appearance has been observed in other pelagic ova seen by 
us. Mr CunnincHam was more fortunate with the ovum of Pleuronectes cynoglossus, 
and he describes a polar globule in this species.§ 
The more obvious features in the living ovum after fertilisation are—(1) The 
meridional streaming of the cortical protoplasm to the animal pole. (2) The formation, 
or, in certain forms, the visible increase in the size of the blastodise, and its assumption of 
a more definite contour. (3) The disappearance of the minute clear vesicles which stud 
the entire cortex of the vitellus, probably as a consequence of the transference of the 
protoplasm to one pole—by which they are carried to the region of the disc. In many 
forms a change in the optical appearance of the yolk is seen. Ransom noticed this, and 
says that the increased clearness and translucency of the yolk is in part due to distention 
and greater transparency of the enveloping layer (No. 127, p. 458); indeed, the whole 
ovum after fertilisation assumes a brighter and more tense appearance. Finally (4), a 
space slowly becomes apparent between the vitelline globe and the inner surface of the 
zona radiata, so that the egg-contents are no longer closely applied to the capsule, as in 
the unfertilised ovum. 
Probably the foregoing features mark the fertilised condition in all Teleostean ova ; 
but there are many forms in which, for various reasons, they cannot readily be discerned. 
* This closure of the micropyle is perhaps incomplete, as the subsequent formation of a perivitelline space is 
due to the entrance of water in the main through the micropyle, though it may also enter by the general surface. 
+ Loe. cit., footnote, p. 190. t Op. cit., p. 597, fig. ii. d. 
§ Op. cit., p. 131, 
