386 FRANK R. LILLIE 
in sea-water and the latter by treatment with KOH prolonged 
to a stage in which only a small percentage of the spermatozoa 
continued to move. Under these conditions in a large number 
of eggs the sperm aster separated from the sperm nucleus, which 
was usually left on one side, and proceeded alone to conjugate 
with the egg-nucleus. Thereupon the cleavage spindle formed 
with the egg-nucleus alone, and segmentation of the egg ensued. 
In the four-cell stage usually, but sometimes in the two or eight- 
cell stage, the sperm nucleus united with one of the segmentation 
nuclei. Boveri concludes from this and other results that the 
fertilizing action of the spermatozoon consists in the introduction 
of a centrosome into the egg. When this has united with the egg 
nucleus, with or without participation of the sperm nucleus, fer- 
tilization would be complete; or with the sperm nucleus alone in 
merogony it likewise completes fertilization. 
Boveri has used the term ‘partial fertilization’ for the phenom- 
enon just described, although he admits that it is a misnomer. 
It is unfortunate that such a significance should have come to be 
attached to the expression, because, as has been shown, my own 
results and those of Ziegler, Wilson and Boveri himself prove that 
partial fertilization in the literal sense really occurs. The vari- 
ous stages of partial fertilization as shown by the results in the 
literature on the subject are: 
1. External contact alone by the spermatozoon producing, 
a. Formation of the fertilization membrane, (Loeb and Elder 
for sea-urchins, Lillie for Nereis). 
b. Maturation and formation of the chromosomes from the 
egg nucleus without spindle, (Lillie for Nereis). 
c. Maturation and cleavage to stereoblastula, (Bataillon: 
hybrid union of eggs of Pelodytes punctatus and Bufo calamita 
with sperm of Triton alpestris). 
2. If the spermatozoon be removed shortly after entrance, 
a. Maturation alone may result, (Wilson on Cerebratulus). 
3Herbst (’07 p. 202 and ’09 p. 277) interprets Boveri's ‘partial fertilization’ as 
a combination of parthenogenesis and fertilization. Such an interpretation does 
not, however, explain Boveri’s account of the behavior of the sperm-centrosomes. 
