No. 463.] STUDIES ON PLANT CELL— VI. 465 
fusion of the gamete nuclei would give material for a larger and 
more highly differentiated nuclear figure in the first cleavage of 
the egg. : 
Williams’ (:04b) observations and conclusions on Dictyota 
are especially intefesting in this connection for he shows that the 
first cleavage-spindles in the parthenogenetic eggs are intranu- 
clear and multipolar, showing no dominant kinoplasmic centers 
while the fertilized eggs form each a well differentiated centro- 
sphere with radiations, exterior to the nuclear membrane, which 
clearly guides the whole process of spindle formation. Williams 
does not hold that this centrosphere comes as an organized struc- 
ture from either sperm or egg but is developed de novo by the 
fusion nucleus as the result of the general stimulus of fertiliza- 
tion. The evidence, then, furnished by studies on fertilization 
in plants, indicates that the chromosomes alone maintain mor- 
phological independence throughout the process of fertilization 
and that the kinoplasmic (archoplasmic) elements play no part iri 
the phenomena as fixed morphological structures but simply con- 
tribute their substance to the general union of cytoplasm with 
cytoplasm, and that any specialized kinoplasmic structures of the 
first cleavage spindle are formed de novo. While it is true that 
the sperm brings to the egg much kinoplasm it may well be 
questioned whether such kinoplasm is a necessary factor in the 
formation of the first cleavage-spindle. It seems more proba- 
ble that the development of achromatic structures in the first 
mitosis following fertilization is due rather to the general stimu- 
lus of cell and nuclear fusion than to particular structures sup- 
plied by either sperm or egg. 
The second phase of Strasburger's theory of fertilization con- 
cerns a separation of the two processes in the sexual act: (1) 
the mere growth stimulus, * vegetative fertilization," that may 
be expected with the union of any two masses of protoplasm, 
and (2) the clearly defined sexual phenomena, ‘t generative fer- 
tilization,” which lies in the union of germ plasm of different 
parentage and diverse potentialities and which leads to the 
inheritance of these characteristics. It seems clear that the two 
processes are really present and can be clearly distinguished. 
But it may be strongly questioned whether the factors charac- 
