V. H. Blackman. 
149 
ON THE RELATION OF FERTILISATION, “APOGAMY,” 
AND “PARTHENOGENESIS.” 
By Vernon H. Blackman. 
A LTHOUGH - the subject of fertilisation (used in its widest 
sense to include all processes involving the fusion or 
association of gametes, i.e., the syngamy of Hartog 1 ) has been closely 
investigated for several decades, yet we are still unable to state the 
exact nature of the process. It is clear, however, that in typical 
exogamous fertilisation with a fusion of gametes from different 
individuals three obvious main results are brought about—a stimulus 
to further development, a mingling of two lines of descent, and a 
doubling of the number of chromosomes (or their equivalents). 
That one of the important results of gametic fusion is a 
stimulus to further development has been recognised for some time 
and has led to the “rejuvenescence” theory of fertilisation. In this 
view the essential reason for fertilisation is to give new life and 
energy to protoplasm exhausted by continuous division ; it is a view 
based on the general facts of fertilisation and the usual inability of the 
sexual cells to develop without fusion. It received very striking support 
from the well known observations of Maupas who found that the 
descendants of single Paramoecium after about the 170th generation 
began to show signs of disorganisation, lost the power of division 
and soon died. When in this “senile” condition they could,, 
however, be restored to their original vigour and power of division 
by conjugation with another individual (though not of the same 
brood). 
These observations pointed clearly to the fact that conjugation 
(fertilisation) brought about some stimulus which restored the 
flagging energies of the organism. The probable nature of the 
stimulus has been made very evident by the brilliant observations 
of Calkins, 2 who found that, if, when the regular period of depression 
occurred in Paramoecium growing in hay-infusion, the organism were 
placed temporarily in beef, brain or pancreatic extract or even in a 
solution of potassium phosphate, the vigour of the cell was com¬ 
pletely restored and when returned to the hay-infusion divided with 
its usual rapidity. By this means Calkins has been able to tide 
Paramoecium over several eras of depression, which would otherwise 
1 Quart. Jour. Microsc. Science, XLVII. (1904), p. 581. 
2 Archiv f. Entwicklungsmech, XV. (1902), p. 139. Archiv f. 
Protistenkunde I. Q902), p. 355. Biol. Bull. III. (1902), p. 192. 
