408 
CHIYOMATSU ISHIKAWA. 
days, until it becomes nearly colourless. This also seems to be 
the case with the eggs ; undergoing similar changes, when 
they are subjected to different external conditions. A case of 
similar nature is also stated to occur in the eggs of Eupa- 
gurus by Dr. P. Mayer where he says (-244) : “Es bestehen 
aber in der Intensitat der Farbe individuelle Abweichuugen, 
wie dies auch schon vor mir andere Autoren beobachtet und 
mit seltener Uebereinstimmung auch stets (ob mit recht?) 
auf Yerschiedenheiten in der Farbung des Mutterthieres 
zuruckgefuhrt haben.” 
Development. 
Segmentation: — The newly-laid egg shows no nucleus, as 
before remarked, but soon a definite one appears in the centre. 
The inner and the outer egg-membranes, which at this early 
date lie so closely together, separate after a lapse of ten to 
fifteen hours, and a certain quantity of albuminous fluid collects 
between them. A similar fluid is stated to occur in the 
Orchestia eggs by Ulianin ( Vk 1 ), where, however, the occur- 
rence is of a much later date, namely, at such stages where a 
fine cuticular skin becomes distinguishable around the embryo. 
This fluid becomes coarsely granular when the egg is treated 
with such reagents as alcohol, acids, &c. It becomes a cause 
of great hindrance for hardening, as has already been pointed 
out by Ulianin ( 4 -4J); and in order to avoid this difficulty I 
have used the same method described by him, by which means 
alone I was enabled to harden the eggs properly. This method 
consists in breaking off' the secondary egg-membrane by means 
of the points of needles under the dissecting microscope, the 
eggs being placed in a watch-glass under water. After the 
greater part of the albuminous fluid has escaped out of the 
slit thus made, the eggs were brought to the hardening fluid, 
which now reaches the embryo easily. 
Segmentation begins by a slight notch on one side of the 
egg transverse to the long axis (figs. 17 and 18). This notch 
gradually elongates both ways, until the egg is divided into 
