io Davis.— Spore Formation in Derbesia. 
have seen some evidence of a centre on the exterior of the nucleus (Fig. 31 ), 
to which the spirem seemed to be attached, suggesting nuclear polarity 
similar to that described by Harper (’05) for Phyllactinia . However, the 
conditions in Derbesia are not very favourable for the study of this 
point, and , I am not prepared to discuss the matter further at this time. 
The spindle at metaphase of mitosis (Fig. 32 ) is intranuclear, and 
there is a minute granule at each pole. 
Cytological Discussion. 
This discussion will concern itself chiefly with the morphology and 
development of the blepharoplast and its relation to the nucleus. There 
is a wide divergence of opinion respecting these problems. Strasburger 
(’92/00), from studies of zoospores, chiefly those of Oedogonium, Cladophora , 
and Vaucheria , concluded that in these forms the cilia were derived 
from a body (blepharoplast) which arose in the outer plasma membrane. 
This conclusion for Oedogonium is of especial interest, since the zoospore of 
this alga is provided with a circle of cilia similar to that of Derbesia. 
Mottier (’04) has described the blepharoplast of Chara as arising in the 
plasma membrane in agreement with Strasburger’s views. 
Timberlake ('02) noted fundamentally different conditions in his study 
of zoospore formation in Hydrodictyon. He described the blepharoplast 
as a body distinct from the plasma membrane and connected with the 
nucleus by delicate fibres. There is also a period during zoospore 
formation when the nucleus lies very close to the cleavage furrow, and at 
this time a granule may sometimes be observed at the side of the nucleus. 
Timberlake did not trace the origin of the blepharoplast, but it seems very 
probable that it is derived from this granule close to the nucleus, and 
remains connected with the latter by delicate fibres, at least during the 
earlier periods of zoospore formation. There is thus an apparent agree- 
ment between Hydrodictyon and Derbesia in the intimate relation of 
the blepharoplast to the protoplasm around the nucleus and its indepen- 
dence in origin of the outer plasma membrane. 
The other studies on the blepharoplast of plants have been con- 
cerned chiefly with its possible relation to a centrosome. Belajeff in a 
series of papers (’97 a , ’97 b, ’97 c, ’98, ’99) described the blepharoplasts of 
Gymnogr amine , Equisetnm and Marsilia. He found the blepharoplasts 
at the poles of the spindles in the mitosis just preceding the formation 
of the sperms and regarded them as centrosomes. Shaw (’98) held that 
the blepharoplasts of Marsilia did not occupy the poles of the spindle 
of the final mitosis, but were formed at the poles of the preceding spindle ; 
Belajeff, however, disputes this. 
