No. 2.] BLATTA AND DORYVPHORA. 425, 
The eggs are deposited by the females in such a way that the 
pole which leaves the vagina first is glued to the surface of the 
leaf by a semifluid secretion, which at this point spreads out 
into a flat disc on which the egg rests and by which it is 
attached. As the hatching larva always leaves the egg head 
foremost at the opposite free pole of the egg, and as there is no 
revolution of the embryo as in Hemiptera, there can be no 
doubt as far as the cephalic and caudal ends are concerned that 
the relations of the embryo to the parts of the egg are the 
same as those described for B/atta. Moreover, the position of 
the eggs on the leaf and the position of the embryo in the egg, 
are sufficient evidence that the eggs are oriented in the ovaries 
of Doryphora with the cephalic pole directed towards the head 
of the mother insect. 
Thus I have found that 4/atta completely and Doryphora cer- 
tainly in part conforms to the “loi de l’orientation de l’ceuf ” 
of Hallez (17), who found that the ova of Hydrophilus and 
Locusta lie in the ovaries with their cephalic ends directed 
towards the head of the mother insect, and that the dorsal and 
ventral surfaces of the egg are predetermined in the ovaries, 
Kadyi’s (23) remarks make it certain that Perzplaneta conforms 
tothe law. In viviparous Aphzdes the same condition obtains, as 
may be gleaned from the plates of Metchnikow (30) and Will 
(52). When micropyles are developed at the cephalic pole of 
the egg, they form a fixed point which is of great assistance in 
observing whether the “law of orientation”’ obtains in a particu- 
lar instance. We have sucha case in Corzxva as described by 
Metchnikow. In this insect (as also in Affzs), the entoblastic 
growth of the embryo somewhat obscures the process; but it 
can be readily seen that when the ventral plate forms, the por- 
tion of it which will subsequently grow out into the procephalic 
lobes is situated at the micropylar pole, which is anteriorly di- 
rected while in the body of the mother insect. The growing into 
the yolk of the embryo tail first brings the head to the opposite 
end of the egg, but during revolution the embryo regains the 
position which it held before the formation of the amnion and 
serosa (see Metchnikow (30), Plates XXVI. and XXVII. 
Pacs.G, 01,20; 25, 27). 
