178 W. Neilson Jones. 
cause a separation of the fluids. On the lines of this analogy, the 
process of fertilization leads to the formation of the “ symbiotic 
organism”—the zygote—from “active” and “ passive ” varieties 
of protoplasm, and, at the same time, brings about the doubling 
of the number of chromosomes: the reduction division leads 
to the separation from one another of the two groups of 
chromosomes that came together at fertilization, but need not 
separate the “ active ” from the “passive” type of protoplasm, or 
in other words, dissolve the hypothetical symbiotic partnership. 
It would seem necessary to assume however that the two 
kinds of protoplasm do become differentiated previous to, or 
simultaneously with, the formation of sex cells or gametes, since 
in these cells can be recognised once again the marked “activity” 
and “ passivity ” characteristics. 
The life history of a plant such as an homosporous fern on this 
basis will be as follows: 
The male and female gametes, consisting of “ active ” and 
“ passive ” varieties of protoplasm (with nuclei, etc.) unite to form 
a symbiotic partnership in the zygote. This partnership persists 
throughout the life of the “ sporophyte ” and throughout the 
formation of spores (which is accompanied by reduction in the 
number of chromosomes). The spores germinate to produce the 
prothallus (gametophyte) still with the duplicate type of proto¬ 
plasm. At a certain stage the prothallus produces antherozoids and 
egg-cells; and since these exhibit the characteristic “ active” and 
“ passive ” traits and a readiness to combine again, we must suppose 
that their production has involved once more segregation into 
the two kinds of protoplasm . 1 
If a flowering plant be considered from this point of view— 
choosing a dioecious species as simplest for purposes of discussion 
—one is met at once by difficulties arising from the confusing 
terminology ordinarily employed. 
1 E. J. Collins has recently described some interesting experiments that 
are suggestive as to the stage in the life cycle at which sexual segregation 
may occur in the Bryophytes (Linnean Society, June 20th, 1918). Cultures of 
Funaria hygrometrica were made and (a) protonemeta were grown from antheridia 
and from perigonial leaves of male “flowers”; (b) plants were raised from spores 
from a ripened capsule. Submitted to similar cultural conditions (at produced 
a sward of plants with male “flowers” only, no sporogonia being formed at 
any time, whilst ( b) produced plants bearing both male and female organs. 
Thus in this case, segregation of male protoplasm would seem to occur before 
the actual production of antheridia or antherozoids. As is pointed out by the 
author, the shifting backwards in the life cycle of the point at which 
segregation occurs until it is coincident with sporogenesis would result in a 
Bryophyte with the “dioecious’' habit. 
