No. 2.] BLATTA AND DORYPHORA. 323 
Eiern von Bythostrephes steigt das Keimblaschen bei Eintritt 
der Eireife in die Hohe, erblasst allmahlich und zeigt zugleich 
an Ejiern, die frisch in den Brutraum iibergetreten sind, den 
Beginn der Spindelbildung zzzerhalb des dann noch scharf her- 
vortretenden Umrisses des Kleimblaschens.” 
The interesting researches of Weismann and Ischikawa (49), 
Leichmann’s (28) recent discovery of two polar globules in Ase/- 
/us and Pereyaslawzewa’s (40) discovery of polar globules in 
Gammarus pecilurus prove that the Crustacea, too, must be 
included under the general law. 
b. The Law of Orientation. 
Though considerable attention has been given to odkinesis in 
Echinoderms and Amphibia, no extended observations of these 
phenomena in the eggs of Arthropods have , been published. 
In view of this fact, r have taken considerable pains to deter- 
mine the paths of the pronuclei and cleavage nucleus in 4/a¢za, 
and have devoted considerable space to their description. 
A perusal of O. Hertwig’s paper entitled, “ Welchen Einfluss 
iibt die Schwerkraft auf die Theilung thierischer Zellen?”’ (21), 
led me to try experiments to prove whether gravitation has any 
appreciable effects in determining the position of the embryo 
in the egg, or whether the position of the embryo with refer- 
ence to the yolk is predetermined long before, during the de- 
velopment of the egg in the follicle. 
It has been shown that the eggs of 4/azta are carried in a hori- 
zontal position after the first day, so that the ventral or germinal 
faces of the upper row of eggs are directed downwards, and 
those of the lower row upwards. As the crista is continuous 
with the right side of the parent’s body, the heads of the em- 
bryos all point to the right’ It occurred to me that by keeping 
capsules in various positions any effects of gravitation on the 
development of the inclosed eggs could be easily determined. 
I accordingly placed capsules in five different positions on a 
block of paraffine provided with holes and grooves to keep them 
firmly in place. To prevent desiccation, the block was kept in 
a camera humida. 
Capsules were kept from fourteen to twenty days in the fol- 
lowing positions : — 
