252 Mottier. — Development of the Spermatozoid in Char a. 
directly to this band. Ikeno figures in colours a mature spermatozoid. 
in which the central, or nuclear portion, is coloured green, while the anterior 
part with the cilia and the posterior end are coloured red. I do not find 
in his text any statement concerning the development of the posterior 
extremity which is undoubtedly of cytoplasmic origin. 
Ikeno discusses at some length the question of the probable homology 
of the cilia-bearer, or blepharoplast, and the centrosome, concluding that 
these structures are homologous in the phylogenetic sense. In the elabora- 
tion of his argument, it seems to me that he ignores or leaves out of con- 
sideration the most fundamental principle, namely, that structures to be 
homologous must have, at least, morphological rank in the cell, i. e. they 
must be organs in the morphological sense. As a matter of fact the 
centrosome is not an organ of the cell with morphological significance. 
In Char a , certain Pteridophytes and spermogenous Gymnosperms, where 
the development of the blepharoplast is best known, there are no centro- 
somes with which to homologize these structures. Even in Marchantia 
where there seem to be both centrosome and blepharoplast, it has not 
been shown that the former is a permanent structure in the cell, since 
it cannot be followed from one cell-generation to the next. Ikeno ex- 
pressly states that, in the aster and diaster stages of mitosis, the centrosome 
is only occasionally to be seen, and in this he is in accord with the observa- 
tions of the writer and Van Hook. Ikeno has, of course, brought forth 
in Marchantia the strongest evidence that has, as yet, been advanced, 
pointing to a relationship between centrosome and blepharoplast, but this 
evidence cannot be accepted as final. The fact that two bodies look alike 
and stain alike in different cell-generations, is not conclusive proof that 
they are the same. Personally I cannot admit that all the bodies that 
Ikeno figures in cells of Marchantia are centrosomes, as similar bodies 
with exactly the same behaviour have been found in cells of plants in 
which it is known with absolute certainty that centrosomes, as understood 
among plants, do not exist. If, on the contrary, we attribute a morpho- 
logical rank and phylogenetic relationship to the substance of which centro- 
somes and blepharoplasts are made, such as kinoplasm, or whatever we 
wish to call it, and if we admit that a morphological differentiation exists 
in the cytoplasm — a view that has much in its favour — then our theory 
will bring all known facts into line. Otherwise it seems that we shall 
be obliged to be contented with facts as they are known, and patiently 
await other facts and unquestionable evidence. 
Summary. 
The spermatozoid of Chara is a spirally coiled body consisting of 
a nucleus and a specially differentiated part of the cytoplasm which exists 
in the form of a thread or band, the blepharoplast, and bears two long 
