3804 PHILLIPS—A REVIEW OF PARTHENOGENESIS.  [0ct. 16, 
of fertilized eggs recalls the periodic ’occurrence of conjugation 
among protozoa, and according to Wesenberg-Lund (1898) and 
Lauterborn (1898) senility is an important factor in determining 
the length of the cycle. That lack of nutrition and the appearance 
of a senile condition are intimately connected seems very probable, 
if we may be permitted to reason from analogy on work done on 
Paramecium caudatum. Calkins, in a recent paper,’ records that 
he has been able to raise Paramcecia for six hundred and sixty-five 
generations by fission, and they were rejuvenated five successive 
times by change of food rather than by conjugation, or as he 
expresses it ‘‘ parthenogenetically.”’ 
VERTEBRATES. 
The question as to whether there is a parthenogenetic develop- 
ment among any of the Vertebrates is one which has been much 
discussed. If there are any cases at all they are cases of partial par- 
thenogenesis, since in no case is it claimed that development goes 
farther than the first few cleavage stages. Bonnet (1899) discusses at 
some length the evidence on this subject, and since he has so well 
reviewed the literature it is not necessary to do more here than 
state the general conclusions to be reached from a survey of what 
has been reported. 
Eggs of Amphioxus lanceolatus (van der Stricht, 1895) show a 
tendency to divide if not fertilized. This is not pronounced. 
Cleavage of unfertilized eggs in the ovary are reported among the 
Gadide by Burnett and Agassiz (cited by Oellacher, 1869), for the 
Sturgeon by Bellonci (1885), and for the Trout by Oellacher (1872). 
Oellacher attributed this to the retention of the eggs for too long 
a time. 
For the Frog and other Amphibia many. investigators have 
claimed parthenogenetic cleavage, since it frequently happens that 
eggs which pass from the female when she is not copulating with a 
male show cleavages, but these are generally irregular. Pfliiger 
(1882) was able to show rather conclusively that such cases are due 
to fertilization of these eggs by spermatozoa in the water which are 
nearly dead, and consequently the development is short and irregu- 
ular. Kulagur (1895) and Bataillon (1900) did some experiments 
1 Calkins, Gary N., 1902, “Studies on the Life History of Protozoa,” III. 
The Six Hundred and Twentieth Generation of Paramcecium caudatum, zo/. 
Bull,, III, No. 5, pp. 192-205. 
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