THE CENTROSOME AND THE BLEPHAROPLAST. 47 
arise de xovo. They do not persist through several successive genera- 
tions of cells, two cell-generations representing the maximum time of 
their duration. In short, the blepharoplast develops merely the cilia 
and forms, therefore, the locomotary apparatus of the spermatozoid. 
No phylogenetic relationship has as yet been shown to exist between 
blepharoplast and centrosome. The fact is that, in those plants in 
which blepharoplasts occur, there are no centrosomes with which to 
show any phylogenetic relationship. The main reason, it seems, for 
regarding the blepharoplast as the homolog of the centrosome is the 
sole fact that the primordia of the former at a certain period of develop- 
ment are provided with a system of radiations, giving them the appear- 
ance of centrospheres. 
The view concerning the origin and phylogeny of the blepharoplast 
as advanced by Strasburger is of interest, since it is the only one that 
seems to take into consideration all the facts. Strasburger derives the 
blepharoplast from the cilia-bearer of the zodéspores and gametes in the 
alge. In the zodspores of certain alga, e. g., Vaucheria, Edogo- 
nium, and others, the cilia spring from a localized thickening of the 
plasma membrane (Hautschicht) at the anteriorend. In Gdogonium 
this kinoplasmic thickening is in the shape of a doublc convex lens, 
from the edges of which arise the numerous cilia. In the large swarm 
spore of Vaucheria the nuclei seem to be intimately connected with the 
formation of the cilia-bearer. The nuclei migrate to the plasma mem- 
brane and elongate in a direction at right angles to the surface of the 
spore. The anterior end of each pear-shaped nucleus comes in contact 
with the plasma membrane. That part of the plasma membrane in 
contact with the nucleus thickens in the form of a delicate concavo- 
convex lens, from two points of which, on opposite sides, spring the cilia. 
The size and shape of the cilia-bearer vary, of course, in different 
alge. Timberlake (’o1) finds a small body at the base of the cilia in 
Hydrodictyon, but it does not seem to be part of the plasma membrane. 
As Strasburger has pointed out, the ‘‘ mouth-piece ” of swarm spores 
and gametes is not to be confounded with the cilia-bearer, since the 
former represents the entire anterior end of the cell free from chloro- 
phyll. It is true that the cilia-bearer is not well known in the sperma- 
tozoids of alge, but transitions show that in all probability the sperma- 
tozoids were derived from male gametes which in every way resembled 
asexual swarm spores. The spermatozoids of Volvox globator are 
regarded as a good illustration of this relation, for in structure they 
occupy an intermediate position between the gametes of alge and the 
spermatozoids of Chara. In Volvox the two laterally inserted cilia 
would seem to indicate that the blepharoplast had undergone a lateral 
