394
N. BALAKRISHNAN NAIR AND M. SARASWATHY
evidence of a probable change from female to male during the breeding
season as reported in Teredo navalis (Grave and Smith, 1936 ; Coe, 1936).
Thus it appears that the proportion of individuals in the two
functional sexual phases changes with the advance of the breeding
season. There is a preponderance of ambisexual males at the beginning
of the breeding season, with an increase in the number of females in
the large size groups collected during the final phases of the breeding
season, probably as a result of a change in sexual phases from male to
female. There is a possibility of self fertilization during the intervening
hermaphrodite period. A second sex reversal after the assumption of
the definitive female phase (Fig. 29) may also occur. The conclusions
reported above are drawn from the data collected during the breeding
season of the species that extends from June to December ; the animals
settled on test panels during July-August.
From October onwards a small percentage of the females examined
histologically showed indications of inactive gonads. There was noticeable reduction in the gametogenetic activity, at lowest level in late
January and in February. During the non-breeding months, from
January to May, specimens examined histologically revealed the
presence ot the following categories of gonads. Indeterminate gonads
where the follicles are not clear and sex not clearly determinable. The
epithelium of the gonad apparently showed no sign of activity. Common during March-April. Among specimens distinguishable as females
at least three types of histological conditions could be recognized.
(1) Ova loose in the follicle with a few oocytes in the cortical region both
undergoing a process of disintegration, and the epithelium apparently
inactive : common during February. (2) Ova free in the lumen of the
lobule with the walls containing proliferating spermatogonia. The
cortical region is apparently active indicating a probable transition
from a female to a male condition : in March. (3) Follicles shrunk but
the cortical layer containing oocytes showing progress of oogenesis :
in May, June and July.
Two types of maIes could be distinguished during the non-breeding
period: (1) with the cortical layer containing spermatogonia and
spermatids and the germinal epithelium showing some activity, without sperms in any of the follicles, common in February; (2) with
active spermatozoa free in the lumen of the lobule and the cortical layer
with primary and secondary spermatids, with few differentiated oocytes
representing an ambisexual gonad, common during May and June.
Thus in Nausitora hedleyi in the estuarine locality of Cochin backwaters during the period January to May the gonads usually are in a
state of apparent quiescence, The unspawned gonadial elements of the
N. BALAKRISHNAN NAIR AND M. SARASWATHY
evidence of a probable change from female to male during the breeding
season as reported in Teredo navalis (Grave and Smith, 1936 ; Coe, 1936).
Thus it appears that the proportion of individuals in the two
functional sexual phases changes with the advance of the breeding
season. There is a preponderance of ambisexual males at the beginning
of the breeding season, with an increase in the number of females in
the large size groups collected during the final phases of the breeding
season, probably as a result of a change in sexual phases from male to
female. There is a possibility of self fertilization during the intervening
hermaphrodite period. A second sex reversal after the assumption of
the definitive female phase (Fig. 29) may also occur. The conclusions
reported above are drawn from the data collected during the breeding
season of the species that extends from June to December ; the animals
settled on test panels during July-August.
From October onwards a small percentage of the females examined
histologically showed indications of inactive gonads. There was noticeable reduction in the gametogenetic activity, at lowest level in late
January and in February. During the non-breeding months, from
January to May, specimens examined histologically revealed the
presence ot the following categories of gonads. Indeterminate gonads
where the follicles are not clear and sex not clearly determinable. The
epithelium of the gonad apparently showed no sign of activity. Common during March-April. Among specimens distinguishable as females
at least three types of histological conditions could be recognized.
(1) Ova loose in the follicle with a few oocytes in the cortical region both
undergoing a process of disintegration, and the epithelium apparently
inactive : common during February. (2) Ova free in the lumen of the
lobule with the walls containing proliferating spermatogonia. The
cortical region is apparently active indicating a probable transition
from a female to a male condition : in March. (3) Follicles shrunk but
the cortical layer containing oocytes showing progress of oogenesis :
in May, June and July.
Two types of maIes could be distinguished during the non-breeding
period: (1) with the cortical layer containing spermatogonia and
spermatids and the germinal epithelium showing some activity, without sperms in any of the follicles, common in February; (2) with
active spermatozoa free in the lumen of the lobule and the cortical layer
with primary and secondary spermatids, with few differentiated oocytes
representing an ambisexual gonad, common during May and June.
Thus in Nausitora hedleyi in the estuarine locality of Cochin backwaters during the period January to May the gonads usually are in a
state of apparent quiescence, The unspawned gonadial elements of the