60 SPERMATOGENESIS AND FECUNDATION OF ZAMIA. 
Which end of the spermatozoid is to be considered the anterior end 
and which the posterior is not an easy question to determine in Zamia, 
if analogy with other forms is disregarded. In the pollen tube and in 
sugar solutions they move both backward and forward, and in their 
rolling, tumbling motion it is hard to recognize any system. However, 
there are several factors which enable us to determine that the apex 
of the spiral must be considered as the head end: (1) The two sper- 
matozoids as developed are attached by the side opposite the apex ot 
the spiral, and in their separation the cilia movement always exercises 
a very perceptible pulling force outward toward the apex of the 
spiral, which gradually results in the separation of the spermatozoids 
(figs. 47a to 47d). (2) In general, the selective end of the spermatozoid 
in free motion is the spiral end. (3) In slowly creeping out of broken 
pollen tubes, as described above, the spiral end usually precedes, but 
this is not always the case. (4) As observed over the neck cells of 
the archegonia, apparently in the process of attempting to enter, the 
spiral end has always been down toward the very small opening. (5) 
In entering the cytoplasm of the egg cell the apex of the spiral is 
always in the lead, as shown by very numerous instances (fig. 56). 
The last two factors are of the greatest importance, and clearly show 
that the spiral end must be considered the anterior end. This, of 
course, is what would be expected from a comparison with the sper- 
matozoids of ferns and mosses, but it is an interesting distinction from 
the animal spermatozoan where the motile organ forms the tail or 
posterior end. 
In his preliminary paper announcing the discovery of spermatozoids 
in Ginkgo, Hirase (61) described the presence of a prolongation of the 
posterior end of the spermatozoid into a tail, an organ not present in 
other plant spermatozoids, so far as known. In the writer’s prelimi- 
nary paper in 1897, on the spermatozoid of Zama (123, p. 20), it was 
stated that ‘‘there is no free tail in Zama, as is said by Hirase to 
occur in Ginkgo.” In his complete monograph in 1898, Hirase (62, p 
123) again describes and figures the spermatozoid with a sharp-pointed 
tail 284 long. He says that since one never discovers the tail in the 
hemispherical spermatozoids at rest in the pollen tube, it seems rational 
to conclude that they are formed almost at the moment of the escape 
from the tube end at the expense of a certain portion of the cytoplasm. 
Ikeno (70, p. 579) was not able to study the living spermatozoids 
of Cycas, but concluded from a study of fixed material that the sper- 
matozoids of Cycas corresponded to those of Ginkgo in the presence of a 
tail. He wrote, ‘*auch ist ein spitziger Schwanz vorhanden, welcher 
weiter nichts ist als die Verlangerung des hinteren Endes des cyto- 
plasmatischen Mantels.” 
The writer’s conclusion in regard to the absence of a tail in the 
spermatozoids of Zama were based on a study of hundreds of sper- 
