Mr. H. Seeley on some new Genera of Fossil Birds. 109 
ovum, a rounded mass composed of a group of small, pale, and 
scarcely visible cells, enclosed in a common envelope, which 
become more and more apparent in proportion as the egg ap- 
proaches the term of its maturity. At this moment it is impos- 
sible not to recognize in these elements the analogues of the 
spermatic cells of which I have described the mode of formation 
in speaking of the development of the viviparous Aphides. 
These cells, indeed, present all the characters, even to the green 
coloration due to numerous small pigment-granules, which I 
have indicated in the latter ; and we may also recognize in them 
even the little daughter cells in which the seminal corpuscles 
will afterwards be developed. These facts evidently indicate 
that the egg has already, while in the ovary, undergone a first 
fecundation, with which the male has nothing to do, and the 
effect of which is limited to the production of the generative 
elements of the future animal. Now the agents of this fecunda- 
tion are nothing but the seminal corpuscles developed in the 
hermaphrodite apparatus of the embryo, and which are trans- 
mitted by the latter to the adult female. 
After fecundation by the male, and the deposition of the egg 
which succeeds this, the embryogenic work, properly so-called, 
commences. The blastoderm appears in the form of a continuous 
layer of cells surrounding the whole surface of the egg. This 
blastoderm opens widely at its posterior part, and the mass of 
spermatic cells penetrates towards the middle of the vitellus. A 
wide canal, which extends from the posterior pole to the centre 
of the egg, marks this passage for some time ; then the orifice of 
the blastoderm closes, and the walls of the canal are effaced. 
But, unfortunately, the egg, which, while these phenomena are 
taking place, has acquired a darker tint at its anterior pole, due 
to the coloration of the chorion, soon becomes covered from one 
end to the other by a blackish veil, which conceals from the 
observer the further phenomena taking place im its interior. 
XIX.—Note on some new Genera of Fossil Birds in the Wood- 
wardian Museum. By H. Seeiey, Ksq. 
TERTIARY BIRDS. 
Ptenornis. 
Sternal end of a right coracoid from the Lower Tertiary of 
Hempstead, Isle of Wight. It has much the size and form 
seen in the Mute Swan; but the exterior angle is rounded and 
thickened, as in Bubo. The bone is compressed; the sternal 
articulation is convex. There is nothing to show whether the 
