56 Sarah M. Baker. 
II. —Effect of Exposure to the Air on the Expulsion of 
Gametes from the Conceptacles. 
The first essential is to have a means of measuring the number 
of reproductive bodies ejected from a definite number of conceptacles 
under various conditions. The method employed was as follows. 
The specimens were collected as the tide ebbed, whenever possible, 
and were left in a large rock pool until required. They were then 
carefully washed, and exposed to the open air, by leaving them 
lying on flat stones on the shore, for definite periods of time. The 
dried receptacles were covered with a measured quantity of water, 
after trimming them so that there were 200 conceptacles in each 
receptacle. After twelve hours the receptacles were removed and 
the number of bundles of gametes in the water was counted. The 
bundles of oospores were sufficiently large to be fairly easily counted 
with the naked eye, or a small lens, when the water was contained 
in a white glazed vessel. The number of bundles of antherozoids 
was estimated by taking out, with a pipette, several drops of 
approximately the same size (after violently stirring the liquid) and 
counting the number of bundles in each drop under the microscope ; 
the mean value of three readings has been used in every experiment. 
The weights of ten consecutive drops of pure water, delivered from 
the same pipette, were found to vary from 00197 gram to 0-0229 
gram per drop, the mean value being 0-0213 gram; so the 
variation in volume of drops is not more than about 16%. The 
pipette used to measure out the water was a short one with a fine 
capillary just above the bulb, so that the liquid adjusted itself 
mechanically to a definite level in the capillary, by means of surface 
tension. This enabled several small quantities of water to be 
accurately measured out in a very short time. The volume of the 
pipette used was found to be 3-348 ccs. which is about 160 times 
the volume of one drop. This method of counting the numbers 
was employed in all the experiments referred to in this paper except 
where otherwise stated. 
The methods are open to several errors:— 
(a) . Errors in counting; these are extremely easy to make 
when the numbers involved are large, and can only be avoided by 
care and system. 
( b ) . Errors due to breaking up of the bundles of gametes can 
be obviated to a certain extent in the case of the oospores, which 
can be roughly counted; and the number of bundles broken up is 
then estimated by dividing by eight for the Fuci and by four for 
Ascophylluni. 
