SOME PROBLEMS OF REPRODUCTION. 3 
PAGE PAGE 
B. The Reproductive Incapa- A. The Modes of Rejuvenes- 
cityof Obligatory Gametes 58 cence. : ‘ Ok 
C. The Adaptation of Gametes B. The Advantages of Karyo- 
to different Fates . . 59 | gamy as compared with 
D. Analytic Summary of Gam- Agamy and Apogamy. 68 
etogenic Processes . 60 
C. Allogamy and Sex . yal 
(Alleged Excretion Pro- 
cesses) : ; 5 6F D. The Origin of Sex . we 
VII. The Causes of Protoplasmic 
Senescenceand Ultimate 
Reproductive Incapacity 64 
HE. Paragenetic Processes, 
usually comprised under 
the term “ Partheno- 
VIII. Protoplasmic Rejuvenes- genesis”. f | 3 
cence, its Nature and 
Modes. : 4 . 67 | IX. General Conclusions . e575 
I. IntRopvucrory. 
THE curious phenomena preceding the maturity of the 
ovum in Metazoa have been the object of much study and the 
groundwork of much theory during the last fifteen years. 
Unfortunately processes occurring in this highly specialised 
group have been assumed to be typical of all organisms; the 
authors who have put forward explanations of what they have 
seen here have too often sought to extend these explanations 
to other groups, where the facts are different; they have 
created homologies where none such exist in Nature, and over- 
looked those which lay under their eyes. In this way proto- 
plasmic changes of various origin and functions occurring in 
Protozoa, Protophytes, and Higher Plants, have been inter- 
preted as excretory processes, in order to make them fit in 
with the replacement theories of fertilisation, founded almost 
exclusively on the formation of the polar bodies in the 
Metazoan ovum. 
A careful study of the accessible materials in the gigantic 
storehouse of facts bearing on this subject has led me to the 
views which will be found in the following pages, namely : 
(1) That the most general, but not universal, feature un- 
derlying the preparations for fertilisation is the specialisation 
