Cell Structure, Growth and Division in tlie Antheridia of Polytrichum etc. 173 
A consideration of our present knowledgeconcerning the blepharoplasts 
may throw some light upon the homologies of the cells in which they 
appear. It was suggested by Belajeff (1899), on the basis of his Observa- 
tion of centrosome-like bodies during the antheridial divisions of Marsilia, 
that every interior cell of the antheridium at any stage of its history is 
morphologically a “spermatid” [androcyte]; and that the reduced number 
of antherozoids in the higher pteridophytes results from the omission of 
the later antheridial divisions. 
In view of the general agreement of more recent investigators that 
blepharoplasts or similar bodies are not present dnring the earlier antheri- 
dial divisions, but that they do appear, at least in many cases,in the penul- 
timate cell generation (the androcyte mother cells), it seems more prob- 
able that it is the androcyte mother cells and the androcytes that have 
been retained in the evolution of the pteridophytes and spermatophytes. 
As we have seen, the androcyte mother cells of Polytrichum differ from 
the cells of earlier generations in several respects, of w r hich the presence of 
a centrosome-like organ is perhaps most noticeable. Apparently some- 
thing of the same sort is true of the penultimate antheridial generation 
in other bryophytes and in the members of the higher groups. Upon the 
hypothesis herein suggested, the reduction in the number of antherozoids 
produced in eaeh antheridium in the higher pteridophytes has residted 
from the omission of some of the androgonial divisions; and a continuation 
of the same process in the evolution of the gymnosperms has eliminated 
all the androgonial generations, the “body cell” being the homologue of 
the androcyte mother cell. That the same is true of the “generative cell” 
of the angiosperm pollen grain is perhaps an unsafe conclusion in view of 
the apparent absence of anything like a blepharoplast; and ourignorance 
of the relationships of the characeae renders of little value any hypothesis 
as to the homologies of their spermatogenous cells. 
The mueh-controverted comparison of blepharoplasts with centro- 
somes or central bodies involves two problems which have not always 
been distinguished: First, are the blepharoplasts of the bryophytes and 
higher groups sufficiently similar in appearance and function to centro- 
somes to be called by the same narne? — And second, are the blepharo- 
plasts homologous with the central bodies of certain thallophytes? 
Upon the former question it has been urged, especially by Belajeff 
and Ikeno, that, as we have seen is the case in Polytrichum, a single body 
divides into two, from each of which spindle fibers grow out, and which 
ultimately lie at the poles of the eompleted spindle; that blepharoplasts 
