SOME PROBLEMS OF REPRODUCTION. 61 
8. When the gametes are unequal the males are usually 
the product of a more complex segmentation than the 
females. 
4, The number of repeated fissions to form the oogametes 
from the oogonium varies, and the divisions may even remain 
in abeyance and the oogonium assume directly the character 
and functions of an oosphere (Volvox, Floridez, Cycas). 
5. Owing to adaptive modification only one gamete of a 
brood may be fertile, and the rest aborted, either arrested, 
or degraded into accessories of the sexual process. Thus in 
Metazoa out of a brood of four gametes three are arrested as 
polar bodies. In the Archegoniate Cryptogams, Conifers, 
and Gnetacee, a similar formation of a single fertile oosphere 
takes place, but the infertile gametes are degraded to form the 
channel for the transmission of the spermatozoon. 
6. The gametogenic divisions may only affect the nuclei, 
cytoplastic fission remaining in abeyance. In such cases 
arrested gametonuclei may remain (a) in the periphery of the 
protoplasm of the fertile one (polar bodies of many Arthro- 
pods); (4) be digested, ejected, or excreted (certain Ciliata and 
Fucacez), or simply degenerate in situ (periplasm of Perono- 
spora, Ophryocystis). 
7. The number of such rejection-nuclei is determined by 
two factors: (a) the primitive number of gametes in the brood ; 
(6) the number of fertile gametes formed and requiring nuclei. 
Thus in Fucaceze, where eight is the primitive number of 
gametes, four, six, or seven sterile nuclei are eliminated, 
according as the number of fertile oospheres produced in the 
oogonium is four, two, or one. 
8. Hence it follows that the number of arrested gametes (or 
rejection-nuclei), being variable, can have no universal physiolo- 
gical significance. 
9. While the specialisation of gametes by fission is the 
rule, gametogenetic fissions do not occur when a vegetative 
cell undergoes direct conversion into an oosphere. 
10. In some Apocytial Plants the gametes are formed by 
the resolution of the apocytium into uninucleate cells, 
