Reproduction in Anthopleura — Ford 
139 
his gratitude to Dr. Cadet Hand, under whose 
guidance this work was carried out, and to 
acknowledge with appreciation his generous help 
with arrangement and discussion of the data. 
MATERIALS AND METHODS 
All living material used in this study was 
collected from an approximately 100-yd length 
of coastline about 4 miles by road south of 
Stinson Beach, Marin County, California (lati- 
tude 37° 52' N), and studies were carried out 
in the Department of Zoology of the University 
of California, Berkeley. 
For the study of the gonad cycle, a population 
of Anthopleura elegantissima was sampled at 
approximately 4-week intervals, except when 
prohibited on two occasions by inclement 
weather or poor tides, for a period of 2 1 months, 
from February, 1959, to October, I960. Several 
individuals were taken from each of several 
rocks, assuring the inclusion of nearly the range 
of sizes to be found. 
The animals were anaesthetized for several 
hours in a 50-50 solution of sea water and 
magnesium chloride isotonic with sea water. 
They were then injected with and preserved in 
Bouin’s picro-formol solution. 
The reproductive state was assayed by de- 
termining the ratio of the estimated volume ( in 
milliliters) of gonadal tissue to the wet weight 
(in grams) of the preserved sea anemone. This 
ratio is referred to as the gonad index, after 
Bennett and Giese ( 1955 ) . 
Before being weighed, the preserved animals 
were cleaned of debris adhering to the column, 
cut in half longitudinally, and squeezed gently 
and blotted on damp paper towelling for about 
Vi minute to remove surplus fluid from within 
the coelenteron. 
The gonads, of which there may be a few to 
more than 100 per individual, develop as thick- 
ened folds of the mesenteries between the 
longitudinal retractor muscles and the mesen- 
terial filaments, and basal to the level of the 
pharynx. To estimate the total gonad volume, 
each animal was dissected to count the total 
number of gonads, which was multiplied by the 
average volume of a sample of 5 gonads. The 
volume of each of the 5 gonads was determined 
by multiplying together the length, width, and 
thickness as measured by a calibrated ocular 
micrometer in a binocular dissecting microscope. 
Bits of each of the 5 sampled gonads were teased 
apart and squashed gently in water and exam- 
ined microscopically. In all but the most imma- 
ture, the gonads from each animal are identified 
either as ovaries by the presence of ova ( 18 to 
about 200 microns in greatest diameter) with 
prominent nuclei, or as testes by the presence 
of vesicles filled with small round spermato- 
cytes (3 to 4 microns), or with tailed sperm. 
Even in the field maturing females can be dis- 
tinguished by the presence of the light chocolate- 
brown ovaries when the animal is torn open. 
However, even nearly mature males ( with tailed 
sperm in the testes) must be preserved and 
dissected to distinguish the milky-white testes 
from the tangled masses of mesenterial filaments. 
To further characterize the reproductive state 
of the females, the greatest diameter of the 
largest ovum found in each of the squashed bits 
of ovary was measured by means of a calibrated 
ocular micrometer in a compound microscope 
and the average was recorded. 
For the study of the distribution of males 
and females on the rocks, a sample of 240 
individuals was taken on July 1, 1961. From 
each of 12 rocks 2 samples of 10 animals each 
were taken from closely packed aggregations on 
extreme sides of the rock, noting the approxi- 
mate distance between the 2 samples of 10, 
and whether they were part of the same or of 
separate aggregations. In the laboratory the ani- 
mals were relaxed, preserved, and subsequently 
weighed and dissected; and the sex of those 
with gonads was determined. 
DISTRIBUTION OF SEXES 
While processing the animals collected in 
1959 for the study of the gonad cycle, it was 
observed that all but a few individuals with 
gonads were unquestionably females, giving a 
sex ratio of approximately 7.5 females to 1 male. 
So on October 5, I960, 100 animals were col- 
lected from the population, 2 groups of 10 from 
each of 5 rocks, as a larger sample for determin- 
ing the sex ratio in the population. However 
the population had apparently entirely spawned 
out, as no individuals were found to bear gonads 
(2 weeks earlier, many animals sampled had 
