1912] CHAMBERLAIN—CERATOZAMIA 13 
Dioon, the average measurements of sperms in the pollen tube being 
220 @ in diameter and 185 in length from apex to base. The 
sperms of Zamia floridana, as described by WEBBER (5), reach a 
diameter of 306 u and a length of 332 », and those of Dioon edule 
measure 230 in diameter and 300 in length. The sperms of 
Cycas and Microcycas are smaller. 
The sperms were often examined in the living condition. They 
are easily visible to the naked eye, and with a pocket lens one can 
see the more general features of their movements, but an examina- 
tion under low powers of the microscope is more satisfactory. 
When exposed to the air, the pollen tubes soon burst, the sperms 
seldom swimming longer than 15 minutes after the ovules are 
opened, but when the ovules are cut transversely, the female 
gametophyte removed, and the cut end placed in a drop of sugar 
solution on a slide, the tubes may be examined for a few seconds 
at a time and thus allow a more prolonged observation. Just 
how long the sperms are in the motile condition was not determined, 
for sperms which have not begun to move when an ovule is opened 
may suffer from the shock, and when sperms are already moving 
it cannot be determined how long they have been motile. Move- 
ments of individual sperms have been observed for 6 hours. 
The movements are like those described for Dioon edule, a for- 
ward movement accompanied by a rotation upon the axis. The 
sperms swim rapidly, bumping against each other and against the 
sides of the tube. When swimming straight ahead the apex is 
stretched out in front (fig. 16), but when the sperm strikes anything 
the apex is often drawn in suddenly, with a movement reminding 
one of the sudden retreat of a Vorticella. So far as the form is 
concerned, the drawings of three sperms shown in figs. 15 and 16 
might have been made from a single sperm at intervals of a few 
seconds. There is also a slower, amoeboid movement of both 
cytoplasm and nucleus. The contour of the nucleus is very irregu- 
lar and is constantly changing. Slender prolongations of the 
nucleus may reach nearly or quite to the ciliated band. 
A few attempts were made to determine whether the sperms 
are chemotactic or not, but no results were obtained. Mrvyake (8) 
reported that the sperms of Cycas show no chemotropism, and 
