14 Davis. — Spore Formation in Derbesia. 
with those of Gurwitsch and Wallengren that the granules at the bases of 
cilia in epithelial cells are not related to centrosomes. 
The Flagellata present excellent subjects for the investigation of cilia- 
forming organs, which in this group have not as yet received the attention 
that they deserve. Plenge (’99) established the presence of a granule at the 
base of the cilium in the swarm spore of the myxomycete, Didymium , and 
the connexion of this granule by a delicate fibril with the nucleus of the cell. 
Similar conditions were also observed by him for several flagellates. 
Dangeard (’ 01 ) has shown in some detail for Polytoma that the two cilia 
arise from a small body connected with the nucleus by a delicate fibril, and 
Maier (’03), p. 145 , confirms his observations, and also reports a similar 
structure in the cells of Chlamydomonas . Prowazek (’03) studied the con- 
ditions in a number of flagellates, finding the cilium in some forms in intimate 
connexion with the nucleus, and in others arising from a granule connected 
with the nucleus by a fibril, or with its base so connected. His observations 
thus support those of Plenge, Dangeard, and Maier. All of these authors 
have discussed the possibility of the basal granule being centrosomal 
in character when comparing these ciliated cells with the spermatozoan, but 
definite conclusions on this subject must await detailed investigations 
on nuclear division and the origin of the cilia in daughter-cells of the 
flagellates. However, it does not seem probable that the basal granule 
is a centrosome. 
There is another phase of the subject of cilia-bearing organs of animal 
cells which must be mentioned, since it indicates that such structures may 
have different origins and developmental histories in different tissues. That 
centrosomes are intimately concerned with the development of the locomotor 
apparatus of the spermatozoid seems to be established from the studies on 
spermatogenesis in animals ; see discussions of Meves (’01) and Waldeyer 
(’06). There is, therefore, a situation with respect to the origin of cilia-bearing 
organs of animal cells apparently somewhat similar to the divergent accounts 
of plant cells. That is, these organs have a relation to centrosomes in the 
spermatozoid but an independence of centrosomes in epithelial cells, in 
those of Infusoria and probably also the Flagellata. Whether the blepharo- 
plast of the plant sperm is related to the centrosome is, however, a matter 
demanding further investigation. 
The Zoospore and Motile Gamete as Taxonomic Characters 
IN THE SlPHONALES. 
Within recent years emphasis has been laid by a number of writers 
upon the zoospore and motile gamete as structures of fundamental impor- 
tance in determining the relationships of great groups among the algae. 
The motile reproductive cells are held to retain in the various groups the 
