1910] HOYT—FERTILIZATION IN FERNS 367 
to enter the egg does not seem to be due to any failure of the sperm 
to perform its part in the process. 
5. The failure of such sperms to enter the egg seems to be due 
either to some hindrance interposed by the egg, or to the interaction 
of egg and sperm. Since no means of hindrance on the part of the 
egg could be detected, it seems probable that this failure of the sperms 
to enter the eggs is due to an interaction of the egg and sperm. Such 
an interaction may be physical or chemical, or more probably both 
physical and chemical. 
6. The movements of fern sperms are complex and varied. The 
reactions of the sperms depend on their physiological state, and this 
depends in part on the past experiences of the sperms. 
7- Sperms have a mechanism of response which is called into 
action by a change of conditions or by an interference with the normal 
movements. In such cases they perform a series of complex move- 
ments and continue these until they die or free themselves from the 
stimulus. 
8. Orientation of the sperms in both the positive and negative 
reactions is usually attained by a series of gradual swingings of their 
anterior ends accompanied by a rotation on their axes, and not by a 
sudden turning toward or away from the stimulant. 
9. The observed movements and reactions seem due to the effect 
of the stimulant on the organism as a whole, and not to the action 
of different concentrations of the stimulant on local parts of the 
organism. 
to. The reactions of fern sperms thus seem to be of the same kind 
as those described for protozoa. 
The author is gratefully indebted to Professor D. S. JoHNSON 
and Professor H. S. JenNrncs, of the Johns Hopkins University, for 
much helpful advice and assistance; to Mr. W. R. Maxon, U.S. 
National Herbarium, for the determination of the species used in this 
investigation, and for helpful suggestions; to Professor W. J. MOENK- 
HAvs, Indiana University, and to Dr. D. H. TENNENT, Bryn Mawr 
College, for permission to refer to their unpublished results; to Dr. 
CaMPBELL WartERs, Washington, D.C., and to Mr. W. N. Crure, 
Joliet, Ill., for assistance in completing the bibliography; and to Mr. 
