spermatozoa, Grain counting was carried out in duplicate
smears, Since there were no statistically significant
differences between the evaluation of grain numbers done
by each observer, the results of their countings were
pooled, Data obtained from the evaluation of 30,000
spermatozoa were analysed at the Computing Center.

RESULTS. The influence of storage of spermatozoa on their
fertilizing ability is demonstrated in Table 1. Based on
these results only three time intervals are included in
the presentation of the ARG evaluations. Since maximal
decline in fertility was encountered in spermatozoa stor-
ed for 72 hr, these spermatozoa, while still possessing
some functional integrity, might be expected to present
pronounced changes also in other respects, while 240 hr
stored spermatozoa should represent the extremes of
changes, Table 2 shows the mean grain count in fresh,
control spermatozoa and in spermatozoa after 72 and 240
hr of storage. The significance of differences in grain
numbers between all intervals were tested by means of
thej{2 contingency table test,

The results demonstrate that there are no signifi-
cant differences in the number of silver grains over-
lying spermatozoa from the control group and the two
storage groups.

Analogous results, i.e. unchanged number of grains/
sperm at all storage intervals, were obtained also with
spermatozoa from ejaculates collected on days 50 to 56
after injection of TdR3H.,

DISCUSSION, The progressive decrease in fertilimding cap-
acity with increasing age of rabbit spermatozoa previ-
ously reported (7) was confirmed. It if evident from
the grain count data that no labelled material has es-
caped from the spermatozoa even under conditions as
drastic as 10 days incubation at 37°C, It seems reason-
able, therefore, to assume that the stability of thy-
mine during ageing of sperm would indicate that no quan-
titative 2oss of DNA has taken place,

Measurements in UV light during spermiogenesis and
transit of sperm through the epididymal canal have con-
firmed the coamstancy of nucleic acids in spermatozoa of
bulls (5) and rabbtts (2,3). The observed decline in
Feulgen positive material of spermatozoa during ageing
in wivo (2,3,5) and in vitro (8) and a similar decline
in the diphenylamine reaction during in vitro storage
(1) may reflect qualitative rather than quantitative
changes of the DNA or DNP molecule. Depolymerisation
of the DNA molecule may be one such possibility. Howeveg
if it does take place during ageing of sperm it appears

to have occured without detectable loss of thymine during
the observed period,

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