The Causes of the Zoning of Brown Seaweeds. 59 
IV.— Fuchs spiralis $ 
Hours Dry 
24 
14 
9 
6 
3 
1 
0 
12 
20 
18 
1 
7 
3 
9 
19 
20 
11 
3 
2 
4 
3 
Experiments 
13 
10 
11 
6 
4 
2 
4 
5 
36 
14 
6 
4 
1 
7 
Means 
12 
23 
13 
4 
4 
3 
6 
FucilS 
spiralis ? 
Hours Dry 
24 
14 
9 
6 
3 
1 
0 
138 
264 
207 
35 
90 
80 
61 
Experiments 
203 
174 
158 
92 
27 
64 
67 
312 
147 
89 
73 
76 
74 
29 
127 
420 
323 
99 
118 
33 
62 
\ 
Means 
195 
251 
194 
74 
78 
63 
54 
The values for the bundles of eggs and sperms were found from 
the same specimens in this species. The experiments have been 
so arranged that a given specimen occupies corresponding positions 
in both tables. It is to be noted that the specimens giving many 
oospores give also, as a rule, many sperms; apparently both kinds 
of gametes ripen at about the same time. The mean values have 
been plotted graphically against the time of exposure (Fig. 1). It will 
be noticed that the curves are all very similar in shape. At a certain 
point there is a rapid increase in the number of bundles liberated 
with time of exposure, followed by an approximately constant value 
varying very little with the time. It looks as though a certain 
length of time of exposure was required to make the mechanism 
efficient, and this appears to vary with each species. In the diagram 
the points at which the mechanism may be said to become efficient 
have been indicated by arrows for each species ; in the case of 
Ascophylhun nodosum the experiments were not carried far enough 
for this point, if it exists, to be reached. The length of time 
required for efficiency increases progressively as the seaweeds grow 
