630 H. GRAHAM CANNON 
38. EGG-LAYING. 
On several occasions the actual laying of the egg into the 
brood-pouch was observed. Hach egg is laid separately as 
a continuous stream of foam. The foam appears to consist 
of more or less opaque drops—probably yolk-spheres and 
transparent colourless globules—presumably oil in a continuous 
mass of protoplasm. Immediately after laying, the egg is of 
an irregularly elongated shape tapering at the end nearest to 
the opening of the oviduct. In a few minutes it has rounded 
itself off and become regularly shaped and almost spherical. 
The oil-drops now commence to coalesce to form one large 
oil-globule. About two hours after laying this large oil-drop 
is most distinct. It is excentrically placed in the egg and at 
this time has a diameter very slightly greater than half that 
of the egg. 
As stated above, the only fixative that was found satisfactory 
for the earliest stages of the egg was Carnoy’s fluid. In sections 
of eggs fixed in this liquid it was possible to recognize, according 
to Gatenby’s diagnosis (5), the following structures: (1) one large 
oil-globule excentrically placed and surrounded by a few much 
smaller globules—these appeared as sections of empty vacuoles ; 
(2) a mass of protoplasm placed almost centrally and on the 
edge of the large oil-globule; (8) a large number of yolk- 
discs staining very faintly with thionin and pervading the 
remainder of the egg; (4) a less number of smaller bodies 
scattered among the yolk-discs and staining deeply with 
thionin—presumably the remains of mitochondria or Golgi 
bodies. 
Lebedinski (9) describes a similar arrangement of materials 
in the egg of Daphnia similis, but does not mention the 
mitochondria. 
An egg-membrane is clearly distinguishable soon after the 
egg has been laid, and it would appear very probable, from the 
fact that the egg is laid as a fluid mass which subsequently 
rounds itself off, that this egg-membrane is produced by the 
egg itself after this rounding-off has taken place. It is not 
