The ovaries of 21 2-year-old Merino ewes at various stages of the oestrous cycle were serially sectioned and all follicles > 0·5 mm in diameter were counted and measured. The mean number of normal follicles > 0·5 mm in diameter was 19· 9 per ewe, of which 8·7 were > 1 mm in diameter. The mean numbers of follicles > 0·5 mm in diameter in 'early', 'advanced' and 'late' stages of atresia were 4· 6, 9· 0 and 12· 3 respectively. Early atresia was rarely seen in follicles < 1 mm in diameter; the greatest incidence was in follicles of diameter 1· 5-2' 5 mm.Volumes of the granulosa, theca interna and antrum were calculated for all follicle sizes and the mitotic index of the granulosa and theca determined. Follicles were classified according to granulosa volume, each class having twice the volume of the preceding class. Estimates of the doubling time of the granulosa were made from the mitotic index and an estimate of mitotic time (0'43 h) obtained by use of colchicine on two other ewes. In all ewes, irrespective of day of oestrous cycle, the rate of growth was slow in follicles < 0·4 mm in diameter; above this size it accelerated to a maximum (doubling time 26-30 h) in follicles O· 7-2 mm in diameter. It was estimated that, on average, a follicle takes about 5 days to grow from 0·5 to 2·2mm diameter, and a further 4 days to reach 4·5 mm diameter. The number of follicles entering the rapid growth phase was estimated to be 3-4 per day. The present data do not support any particular 'wave' theory of follicular development, but indicate that follicles are growing or regressing asynchronously at any given time during the luteal stage of the oestrous cycle.At 48 h after treatment of two ewes with PMS gonadotrophin (PMSG), the number of follicles > 0·5 mm in diameter was increased, the greatest proportional increase being in those > 3·5 mm in diameter. Relatively few follicles were undergoing early atresia. At 18 h after RCG treatment (given 48 h after PMSG to two ewes) all follicles> 3·5 mm in diameter were undergoing luteinization and two-thirds of the follicles between 1 and 3·5 mm in diameter were undergoing early atresia.

SummaryData are presented to show that there are three serum fl-globulin types in laboratory mice controlled by a pair of alleles. Each allele appears to give rise to three electrophoretically distinct zones in starch gel. Within the inbred strain AI AGS there was variation between mice in the intensity of staining of the three zones. Reciprocal mating data gave no evidence of an effect of fl-globulin type on segregation ratios as has been reported for cattle.

SummaryThe observations described concern the number of sperms seen within the eggs of the rat, mouse, rabbit, sheep, and dog.A frequency distribution is presented for the eggs of 251 rats and 20 mice, according to the number of sperms that they were found to contain.Considering the high proportion of penetrated eggs in both the rats and the mice, the number of eggs that contained more than one sperm (about 20 per cent.) was much smaller than would be expected if the distribution were controlled by chance alone. This is interpreted to mean that the penetrability of the zona pellucida to sperms decreases after the entry of the first sperm. Such a reaction has not previously been demonstrated in the zona pellucida. In eggs that contained two sperms, the points of entry through the zona were seen much more frequently in opposite hemispheres than in the same hemisphere, an observation that suggests the zona reaction is a propagated change. It is estimated that the mean time the reaction takes to reach completion is not less than 10 min or more than llf-2 hr.In the rabbit the penetrability of the zona pellucida is not influenced by sperm entry. The mean number of sperms in the perivitelline space of the rabbit egg increased from 0·2 10 hr after coitus to 61·8 16 hr after coitus; thereafter there was no significant change.No sperms were detected in the perivitelline space of 12 fertilized sheep eggs or in 12 fertilized dog eggs, although numerous sperms adhered to the surface of the zona pellucida. The zona pellucida of both sheep and dog eggs apparently reacts to the entry of the fertilizing sperm in such a way as to preclude further penetration.Published reports on the number of sperms within the eggs of various mammals are reviewed. It is concluded that, except in the eggs of the rabbit and perhaps the mole, the zona pellucida of mammals reacts to sperm penetration in such a way that few, if any, extra sperms can enter the eggs. The importance of this reaction in relation to fertility is discussed.

Equol (7,4'-dihydroxyisoflavan), a metabolite in sheep of the dietary isoflavone formononetin, was found to be oestrogenic in mice. By subcutaneous administration it had about one-quarter of the activity of genistein. Equol (35–68 µg/100 ml) was found in the peripheral blood of sheep 4–24 hr after first feeding with red clover (Trifolium pratense) pellets, and represented 9–68% of the "free" and 23–72% of the conjugated "phyto-oestrogens" in the plasma. In ewes grazing red clover, equol was found in the plasma (50 µg/100 ml) and in the uterine tissue (46 µg/uterus) and represented in both instances more than 70% of the extracted "phyto-oestrogen". It is concluded that equol is probably of major importance in relation to the oestrogenic activity found in sheep ingesting clover with a high formononetin content. In guinea-pigs, equol (32–71 µg/100 ml) was found in plasma samples 4–16 hr (day 3) after feeding with red clover pellets. Another probable metabolite of formononetin, referred to as metabolite "A" and tentatively identified as demethylated angolensin (2,4-dihydroxyphenyl-p-hydroxyphenylethylketone), was also noted in the plasma of sheep and guinea-pigs after ingesting red clover.

Pure genistein, biochanin A, and formononetin when administered to ovariectomized ewes by intraruminal (i/r) infusion appear to have oestrogenic activities of the same order. Coumestrol given similarly has activity about 15 times as great. Genistein, biochanin A, and coumestrol appear to be considerably less active when given i/r than when injected intramuscularly (i/m), but formononetin is more active i/r than i/m. This may be related to the lower solubility of formononetin. Examination of the urinary phenols before and after treatment showed that almost all the administered isofiavone underwent metabolic degradation. Genistein and biochanin A appeared to be largely excreted as p-ethylphenol, but only about 5% of the formononetin was accounted for as detectable metabolites, of which a major one was equol.