410 
CH] YOMATSU ISHIKAWA. 
A similar case of segmentation is stated to occur in the egg 
of Lucifer by Brooks 
The segmentation to this stage may thus be compared to the 
first segmentation period of Mayer ( - ° - 5 ~ 2 - 2 - ! ). After this it 
goes on regularly. Each of the eight spheres is now divided 
into two by the second set of equatorial furrows, and the egg 
therefore consists of sixteen equal spheres (figs. 32 and 38). 
In each of these the protoplasm takes the peripheral position 
and the deutoplasm the central. The nuclei of the egg can 
now be seen on the surface. After a pause a third set of longi- 
tudinal furrows appears almost simultaneously, and divides 
the egg into thirty-two parts (fig. 33). The central deuto- 
plasmic portion of each segment now segments off from the 
peripheral protoplasmic and form “ yolk-segments ” (Bal- 
four '-j^) of unequal sizes (fig. 39, ysg.), the cells arranged 
at the periphery being well marked from these segments. 
This seems to be an exception to what is generally seen among 
the Decapod eggs, where the apices of the segments, at such an 
early stage, are usually fused in the deutoplasmic mass in the 
centre of the egg, the mass showing no distinct divisions into 
segments. Transverse furrows now divide the egg into sixty- 
four parts. New yolk- masses are separated off from the 
segments. Longitudinal furrows again divide the egg into 
128 parts (fig. 34). After the egg is divided into 256 parts 
by new furrows, its shape becomes spherical and the segmenta- 
tion unequal. 
Now the segments at a small area near one pole of the egg 
divide faster than the rest (figs. 41 and 42). This area is 
depressed a little, and the egg appears bean-shaped when 
viewed from the side. A section of this stage shows a row of 
lenticular cells near one pole (fig. 40, b l ), separated from the 
yolk-mass, while the nuclei at the rest of the egg- periphery 
still occupy their position at the surface of the pyramidal cells. 
Each “yolk-segment” (figs. 40, 43, 51, and 53) contains a 
number of yolk-spheres and clear vacuoles. The yolk-spheres 
are normally oval in shape, but become polygonal in hardened 
specimens. The vacuoles are of varying sizes, often very 
