SOME PROBLEMS OF REPRODUCTION. 35 
passes directly into the oosphere,! and the “law” breaks down 
in our very next group also. 
The spermatozoa of this group are multiciliate, not flagel- 
late; a certain amount of cytoplasm is left over in their 
differentiation from the spermatocytes. 
E. SipHonocamM& (PHANEROGAMS). 
1. Gymnosperms. 
In Gymnosrerms the pollen-grain or androspore pro- 
duces a few sterile cells at its base, which are recognised as 
equivalent to the male prothallus of a Heterosporous Crypto- 
gam. One cell, probably equivalent to the initial of an antheri- 
dium, grows out into the pollen-tube; its nucleus divides into 
two nuclei, one of which is the gametonucleus; or into a 
number of nuclei; so that the pollen-tube represents an 
apocytium of microgametes. 
The formation of the archeg onium is similar to that of the 
Vascular Cryptogams ; the initial cell only forms the neck-wall 
and inner cell, the belly-wall being formed from the neigh- 
bouring cells of the prothallus (so-called endosperm). But 
the gametogenic processes are still further reduced, for in 
Conifers and Gnetads the inner cell only divides once, forming 
directly the oosphere and single canal-cell, while in Cycads the 
inner cell does not divide, but assumes directly the character 
of the oosphere,” a cytoplastic beak-like process replacing the 
canal-cell. Thus, in the series of archegoniate plants in 
Vascular Cryptogams two mitoses specialise the oosphere from 
the inner cell ; in Conifers and Gnetads one mitosis suffices; 
in Cycads none takes place. This variation is a sure proof that 
there can be no need of these mitoses to eliminate part of the 
egg-nucleus and make room for the male, and that the func- 
tion of these mitoses is not that assigned to them in the 
“ replacement ” hypotheses. 
1 “Qn the Development of Pilularia globulifera,” &c., in ‘Ann. of 
Bot.,’ ii, pp. 247-8. 
? According to Eichler, in ‘Engler and Prantl,’ op. cit., vol. ii, §.1, p. 16, 
