93 
Cutler ia multi ft da ( Grev .). 
that, as It has not only a wider geographical, but higher 
tide-mark distribution, in virtue of its greater power of 
resistance to extremes of temperature and wave-action, and 
is moreover perennial and capable of reproducing its like, 
Aglaozonia has even a better claim to be regarded as the 
most important of the two forms, and therefore more entitled 
to be regarded as the phylogenetic and theoretical gameto- 
phyte than the delicate, sexual Cutleria- shoot itself. To 
this view, however, there are serious morphological objections. 
In comparing the development of the two stages, it becomes 
evident that not only is there no special evidence of alter- 
nation which could be included under a theoretical alterna- 
tion of generations, but that even the polymorphism is less 
evident than at first sight appears. 
It is important to note that this polymorphy originates 
only in the embryonic history, leading to the formation of 
the embryos designated the Foot-Embryo and the Protone - 
matoid Embryo respectively; and it is in this that its impor- 
tance lies. Thus, as far as present data go, the dorsiventral 
Aglaozonia cannot recreate the erect plant vegetatively, nor 
can the adult Cutleria reproduce from the base of its main 
axis, clothed with rhizoids to form a secondary holdfast, 
the dorsiventral basal lobes ; although a longitudinal section 
of the attachment-disc shows that at the extreme base it 
never gets beyond the simple segmentation of the foot 
(Fig. 10). 
While the protonematoid embryo is clearly on the way 
to a true Cutleria- form, it is the foot-embryo which is 
aberrant in development, in that it presents an anomalous 
cessation of terminal growth at an early period ; and thus 
the cause of polymorphy may possibly be sought in the 
solution of the problem as to what induces this arrest of 
a free-growing axis : that is to say, — Have we to do with 
the influence of environment on the germinating spore itself, 
or does it act upon the parent organism? Now, in com- 
paring the April cultures of Aglaozonia with the September 
cultures of Cutleria , at Plymouth, it is difficult to see what 
