270 EXPERIMENTS AND OBSERVATIONS 
and are stained. In ova larger than ‘3 mm. I am unable to dis- 
tinguish the vitelline nucleus in the yolk. The latter forms in the 
egos of Syngnathus in a manner different from that described in 
the plaice. It does not form a definite external layer gradually 
thickening towards the centre of the ovum, but appears uniformly 
throughout the protoplasm in small, not very distinct or refringent 
granules, which increase in number and size. In the larger ova 
the yolk appears as large rounded spheres in the meshes of a proto- 
plasmic network. 
To turn now to the examination of these ova by means of sections, 
I have found it very difficult to preserve the ova satisfactorily for 
cutting. The vitelline nucleus is usually preserved, but either the 
germinal vesicle or the protoplasm or both are more or less destroyed 
by the preserving reagents. I have found in this case, as with the 
ovaries of flat fishes, that the much-vaunted mixtures of Flemminge— 
namely, chromic, osmic, and acetic—are not satisfactory, and that the 
fault lies in the acetic acid, which causes shrinking of the nucleus and 
destruction of its delicate reticulum. Chromic and osmic alone, when 
the chromic is not too strong, have a good effect, but have the dis- 
advantages of contracting the nucleoli, preventing staining, and 
making the yolk hard and brittle. Corrosive sublimate, either alone 
or with acetic acid, produces quite disappointing results on the ovaries 
of pipe-fishes. 
In none of my sections have I seen the modifications of the 
vitelline nucleus described by Henneguy, although I have used 
the preserving reagents and stains which he employed, namely, 
Flemming’s mixture and safranin or hematoxylin. I have also 
used the triple stain safranin, gentian violet, and orange G, 
After some modes of treatment the vitelline nucleus is stained, but 
never granular. ‘The largest egg in which I have seen the body 
is ‘36 mm. in diameter, and in this it is as definite in outline and as 
simple in structure as in the small unyolked ova, I have seen no 
indication of modifications tending to the breaking up or disappear- 
ance of the nucleus ; in the larger eggs I can find no trace of it. 
As to its earlier history, it is seen in eggs ‘06 mm. in diameter in 
direct contact with the exterior of the germinal vesicle. In one egg 
there are two of these bodies at different parts of the membrane of 
the vesicle, one smaller than the other. In smaller eggs I have 
seen no trace of it. These smaller eggs form a cluster or nest at 
the very apex of the germinal lamella. As to their origin, I have 
not been able to get sections which show them as perfectly as I 
should wish, but I have seen primordial ova in the epithelium cover- 
ing the apex of the lamella, and that is the source from which they 
all spring. 
