PROCESS OF FERTILIZATION IN THE CRAB ior 
slightly concave side of the one shown in figure 116 indicates 
that it is related to the nucleus shown in figure 112. In this 
case it would be the male pronucleus. The nuclei have grown 
rapidly and continue to do so until they reach the center of 
the egg. Their contents are finely granular. These granules 
increase in size as the nuclei become larger. Figures 118 and 
119 show the position of the nuclei four hours after spawning 
and figure 120 (from an egg six hours old) shows them lying side 
by side in the center of the egg. They have become elongated 
and many times larger than they were when first formed. From 
the above description of fertilization it is evident that the nuclear 
cup takes no part in the formation of the male pronucleus, for 
the latter is derived from the sperm-vesicle which is the inverted 
capsule. 
This completes the description of the structure and behavior 
of the male cells in the stone crab. We have here something 
unique in the method by which the sperm enters the egg and 
something exceptional in the phenomena of fertilization. These 
observations raise several theoretical questions, some of which 
we will now briefly consider. 
9. DISCUSSION 
We have here a case in which an infolded vacuole which arose 
in the cytoplasm is everted through the shell of the egg and 
fertilizes it. How may such an event be brought into harmony 
with the existing theories concerning the chromosomes? In all 
other cases of fertilization the nucleus with its chromosomes or 
at least its chromatin is considered the essential thing; the bearer 
of the paternal qualities to the egg. The part that they play 
in the theories concerning heredity is too important and useful 
to be lightly discarded. But, granting all that is claimed for the 
chromosomes, we are nevertheless face to face with the fact that 
in most cases they disappear during the telophase and are re- 
formed in the next prophase of cell division. Between the miotic 
divisions they can be followed from one spindle to the next and 
in some other cases, some investigators have claimed to have 
