537 
peculiarities were found which seem worthy of being recorded. In 
the youngest ovum observed (Fig. 2) the equatorial plate was not 
Se | rt | a 
X Sie SSSR 
US Bo eee EOS. ER, 
Fig. 2. Karyokinetie spindle just before the completion of the equatorial plate. 
quite complete, though the chromatin was grouped in the vicinity of — 
the equator of the spindle, and occurred in the form of a large number 
of particles, some of which were spherical, others dumbbell-shaped, and 
others again rod-like, while a few had the form of minute spherica, 
vesicles. At either end of the spindle there was a clear circular areal 
the astrocoel, traversed by a few radiating achromatic fibres which 
had their origin in the vicinity of a centrosome and appeared to 
branch somewhat toward their distal end. Each centrosome was 
composed of several deeply staining bodies so closely aggregated that 
their number could not be determined. No granular layer (cortical 
zone) could be detected, nor was there any perceptible extension of 
the astral rays beyond the astrocoel into the cytoplasm. 
In the stage in which the equatorial plate was complete the 
chromosomes were moniliform rods placed parallel to the long axis of 
the spindle, and their number was very much less than that of the 
chromatin particles in the preceding stage. It is presumable that the 
spherical, dumbbell-shaped and rod-like particles unite together to 
form a definite number of chromosomes, probably sixteen, though I 
was not able to make a certain count of them. The astrocoels were 
at this stage considerably larger than before, and the centrosomes had 
likewise increased in size, showing a number of darkly stained particles 
imbedded in a substance which held a certain amount of the stain, 
though much less than the chromosomes or the centrosome particles. 
The astral rays had now extended out a considerable distance into 
the cytoplasm and their continuity with the cytoplasmic reticulum could 
be plainly made out. 
In a still later stage, the latest I observed, the chromosomes had 
almost reached the poles of the spindle (Fig. 3). The size of the 
