Igo! | GAMETOGENESIS AND FERTILIZATION IN ALBUGO 247 
confusion in the case of the multiovulate (vieleiig) oogonia, nor 
in cases where the egg is clearly differentiated in a surrounding 
periplasm; neither should they in forms like Vaucheria and 
Oedogonium. 
The migration of antheridial nuclei into the tube seems to be 
independent of the developmental condition and metabolic 
activity of the oogonium, and is probably due to a negative 
rather than positive chemotropism, possibly of such a nature as 
that suggested by Hartog (1888) for the sporangia of the Sapro- 
legniaceae. The objections raised by Humphrey (1892) to 
Hartog’s view do not find application here, since he was con- 
sidering cases where the sporangium failed to expel any of its 
spores. In Pyronema, where a condition similar to that of 
Albugo often prevails, Harper (1900, p. 362) explains the 
migration of some antheridial nuclei and the passivity of 
others by assuming that “the chemotactic or other stimulus 
which leads the male nuclei to migrate through the tube to the 
oogonium would in this case be assumed to have exhausted 
itself when a number equal to the number of egg nuclei had 
reached the oogonium.” Such an hypothesis does not appear 
adequate for Albugo, for to assumé that a stimulus which can 
arouse a given number of nuclei to migrate cannot bring the 
Same activity to a greater number presents serious difficulties, 
and the supernumerary males are not found em rouse, as would 
be the case if they were stopped when the female nuclei have 
consorts and the hypothetical stimulating agent has been 
exhausted. The failure of some nuclei to leave the antheridium 
is more probably due to a lack of irritability on the part of some 
sperms than to a lack of the stimulating substance. 
The phenomenon of the passage of nuclei from the body of 
the antheridium into its tube is no more comparable to the seek- 
ing of the female by a sperm than is the emptying of an algal 
Sporangium, or an antheridium of the mosses or ferns, or the 
Passage of the nuclei and cytoplasm from a pollen grain make 
the tube, all of which are clearly independent of chemotactic 
influence originating in organs of opposite sex, inasmuch as 
