342 
Faull . — The Cytology of 
centrosome and continues progressively until completed at the opposite 
pole.’ Possibly there is a cleavage in this layer resulting in the plasma 
membrane of the spore and a corresponding membrane lining the cavity in 
which the spore lies. 4 The astral rays never appear to fuse, as is stated 
by Harper to be the case in Erysiplie and Lachnea! Fraser and Brooks 
(’09). These authors describe * an outward flow of some substance 
which emanates from the centrosome ’ in Ascobolus and Lachnea. 4 It has 
already been suggested they add, 4 that this substance is not improbably 
an enzyme.’ This layer is the seat of a cleavage resulting in the two 
membranes mentioned above. 4 We have, however, obtained no evidence 
of a lateral fusion of astral rays to form a membrane such as Harper 
describes, but we hold rather that the rays indicate rather the direction of 
flow of altered substance from the centrosome.’ Berlese (’99) first sug- 
gested the possible directive action of the astral rays in laying down the 
limiting plasmatic spore membrane. 4 II cinoplasma determina poi la forma- 
zione dello strato parietale plasmatica dell’ ascospora, ed individualizzaquindi 
questa il sen al trofoplasma.’ Dangeard (’07) could not differentiate the 
astral rays in his preparations of Pyronema, but he did detect a homogeneous 
sheet of material that issued from the central body and gradually delimited 
the spore. 4 II y aurait peut-etre lieu de modifier legerement la description 
classique donnee par Harper du mode de formation des ascospores dans 
l’asque et du role des filaments de Taster ; ici nous n’avons pas vu de 
filaments, mais seulement cette substance homogene chromatique qui 
enveloppe le noyau progressivement.’ Brown (’ll) affirms that the astral 
rays of Lachnea do not fuse to form the limiting membrane of the spore, 
and that they constitute no part of it. He also finds a membrane lining 
the cavity in the epiplasm in which the spore lies. Evidence from these 
independent sources indicates that Harper’s interpretation of the part 
played by the astral rays of the last mitosis was incorrect. Moreover, 
from a physical standpoint Harper has affirmed an impossibility, as these 
long astral rays swinging down and out separate farther from one another 
(I refer to adjacent rays on the same side of the central body) rather than 
come into contact. Were they all laid side by side and welded into a ribbon 
they are so few and so tenuous that they would form a very small portion 
of the entire protoplasmic membrane of the spore. There is unanimity on 
one fact in this connexion described by Harper, namely, that the limiting 
membrane is formed progressively, but this feature is not more important 
than the determination of the origin of the membrane, as an exact know- 
ledge of the latter must influence our conception of the homologies and 
phylogeny of the ascus itself. 
After the spores are delimited in Laboulbenia , the flask-shaped nucleus 
continues to elongate until the neck is extremely attenuated (Fig. 64). In 
fact, the venter almost comes into contact with the opposite end of the young 
