A rchegonium ; and on Spermatogenesis in Polytrichum. 127 
The Escape of the Ripe Spermatozoids. 
Free spermatozoids have been found unexpectedly difficult to obtain. 
In from seven to ten minutes after a drop of distilled water has been placed 
upon the open cup-like antheridial rosette, one or more rope-like masses are 
seen to arise from the bottom of the cup. These emerge from between the 
numerous imbricating involucral leaves whose tips form the sides and floor 
of the cup. On transference of the drop of water to a slide by means 
of a pipette, the cylindrical masses break up into fragments of various 
sizes. Fig. 41 was drawn from a single small fragment. Each fragment 
consists of a mucilaginous matrix in which occur numerous spherical 
cavities. In each cavity is a spermatozoid in active movement. The 
mucilage is the result of the swelling of the outer layers of the thick walls 
of the spermatids, while the innermost region of the wall remains firm and 
tenacious and forms a delicate vesicle within which the spermatozoid is 
imprisoned. These vesicles are easily demonstrated by covering the drop 
with a cover-glass, when many of them are separated from the mucilage and 
are dispersed in the surrounding fluid. The spermatozoid is coiled within 
this bladder-like sac with its body pressed against the wall, and occupies 
about one and a half turns of a spiral. Fig. 41 shows a spermatozoid 
at this stage. The cilia whose rapid vibration renders them invisible are 
not shown in the drawing. Shortly after the escape of the mucilage from 
the antheridia, the spermatozoids, lying within their vesicles, commence 
a rapid movement, the narrow or ciliated end advancing foremost. When 
this movement is sufficiently rapid, the outward pressure exerted upon the 
wall of the vesicle 'Would bring about its rupture and free the spermatozoid. 
This, however, does not seem to be a common occurrence. In experiments 
performed in the laboratory, only an occasional spermatozoid succeeds 
in liberating itself. Many antheridial cups were treated in the manner 
described without the escape of a single spermatozoid from its vesicle. 
Antheridial cups were filled with tap-water and with distilled water, treated 
in various ways, such as filtration through animal charcoal, thorough 
shaking with air and with oxygen, and the addition of cane sugar ; but by 
none of these methods were the spermatozoids stimulated to make their 
escape. The best result was obtained by the use of rain-water collected in 
a vessel placed upon the roof of the University of Leeds during a Sunday 
morning after forty-eight hours of continuous rain. Under these conditions, 
the rain-water of Leeds would most nearly resemble that of the districts 
where Polytrichum flourishes and succeeds in forming sporogonia. The 
spermatozoid sketched (Fig. 42) resulted from this experiment. During 
several visits to Sedbergh in north-west Yorkshire made with the intention 
of determining the effect of local rain upon the escape of the spermatozoids, 
the weather unfortunately remained fine, and rain did not fall during any of 
