The Origin of Triple Fusion. 281 
four nuclei which lie more centrally in the sac, i.e., egg-nucleus, 
polar nuclei and upper antipodal nucleus, as four gametes. 
According to Dr. Porsch’s view, the two polar nuclei are the 
equivalents of the two ventral canal nuclei. But of all the nuclei 
associated with or forming part of the archegonium in Gymnosperms, 
the ventral canal nucleus is the one which shows, as a rule, least 
vitality, and that there should exist a tendency for two precisely 
similar nuclei of low vitality to fuse together, seems most improbable. 
Also it seems unaccountable that the antipodal egg should have lost 
all affinity for the second sperm nucleus, while the antipodal ventral 
canal nucleus should have developed such an attraction, particularly 
in chalazogamic families, which Dr. Porsch regards as primitive. 
The suggestion that the ventral canal nucleus may be the 
homologue of the upper polar nucleus, has been brought forward by 
Miss Thomas in a historical sketch of “double fertilization” in 
“ Science Progress ” (5). In this case it may be conjectured that the 
original lack of vitality is made good by fusion with a nucleus of 
differing nature, or that possibly the latter supplies some element 
necessary, in most cases at least, to make fertilization by the second 
male gamete effective. For it is evident that though both the ventral 
canal-nucleus and the upper polar-nucleus are sisters of the 
functional egg-nucleus, they are not equivalent to it. 
This latter view then accounts for the relationship of the egg 
and upper polar nucleus, and a physiological reason for the occurrence 
of triple fusion is, perhaps, indicated by it. But direct evidence that 
the ventral canal nucleus ever fuses with another nucleus of any 
kind is wholly wanting, and the opinion that it is occasionally 
fertilized rests on rather a slight foundation, for even that based 
upon Dr. Land’s observations of nuclear divisions in the apex of 
the archegonium of Thuja (6) is somewhat weakened by the fact that 
it was found to divide before as well as after fertilization. 
As an alternative to this hypothesis, it may be pointed out that 
earlier in the history of the Gymnosperm ovule we have another 
series of sister-nuclei, which may equally well be homologized with 
those of the Angiosperm embryo-sac. In Ephedra there can be 
distinguished, among the free nuclei found, prior to the formation 
of the prothallial tissue, a small group lying at the apex of the 
sac, which gives rise to the archegonial region, i.e., that consisting of 
archegonia and jacket ceils. These nuclei may be divided into two 
classes, those, which, after forming short alveoli, undergo but one 
division, so that the alveolus is divided into but two cells, the 
