No. 393-] REVIEWS OF RECENT LITERATURE. 753 
foreshadowed by the presence of the centrosomes during the growth 
period. Two hemispherical spermatids are thus formed, each con- 
taining a large nucleus and centrosome. Each spermatid metamor- 
phoses into a motile (ciliated) spermatozoön of about the shape of 
the spermatozoon of Ascaris, so well known to zoölogists. During 
this metamorphosis the centrosome resolves itself into an elongated . 
band-like structure in the cytoplasm ; from one side of it radiations 
are seen projecting. A process of the nucleus is for a long time 
directed outward toward the deep end of this band, indicating that 
the nucleus is concerned in the changes which are taking place. The 
centrosome band ultimately comes to lie in a long spiral of about 
five turns just under the curved surface of the cell. The cytoplasmic 
radiations emerge from the surface as a spiral band of cilia, which 
remain attached to the centrosome band as to a basal plate ; they 
form the locomotor apparatus of the spermatozoön. The greater 
part of the mature spermatozoön consists of a large nucleus, which 
is covered with a thin but perfectly distinct layer of cytoplasm, in 
which lies the centrosome band bearing the cilia. 
Ikeno regards the centrosome band as homologous with the middle 
piece of the animal spermatozoön, the centrosome being known to 
pass into the middle piece in animal spermatogenesis ; the cilia he 
regards as corresponding with the flagellum of animal spermatozoa. 
In fertilization a spermatozoön makes its way through the fluid which 
has accumulated around the egg-cell, bores into the egg-cell and loses 
its cilia and cytoplasm, after which its nucleus moves toward the oval 
egg nucleus, sinking into a ready formed depression (Empfängniss- 
höhle) on its peripheral end. The sperm and egg nuclei now fuse 
completely, no centrosome being visible during the process, nor in 
the nuclear division which follows. In this division the spindle 
fibers do not converge at either end of the mitotic figure, but lie 
parallel with each other throughout their whole length. The entire 
absence of centrosomes during fertilization is strongly in contrast to 
what is known of fertilization in animals. W. E C. 
Botrytis and its Host. — The relation of Botrytis to its host 
plants has recently been studied by Nordhausen.! With some pre- 
liminary account of the infection of living plants by this fungus 
through the surface of wounds, where by reason of the injured cells 
Botrytis may readily begin its usual saprophytic existence, he passes to 
1 Nordhausen, M. Beiträge zur Biologie parasitärer Pilze, Jažrė. f. Wissen- 
schaft, Botanik, Bd. xxxiii, pp. 1-46. 
