1. The recommencement of the sexual rhythm from deep anoestrus, is described in barren pony mares. Follicular development and oestrus follow after an interval of preliminary changes in the ovaries and accessory reproductive organs.

2. The onset of oestrus can be accelerated by general irradiation with strong artificial light. Local irradiation with a mercury vapour lamp has no effect on the ovaries.

3. Pregnant matings will result from such artificially induced heat periods provided that ovulation is induced.

4. Doses of less than 10 c.c. of sperm injected will cause fertilization when ovulation is so induced.

5. There is a close connexion between the shedding of the coat and renewed ovarian activity.

6. The stimulus to the ovaries probably passes through the eyes as in the ferret.

The blood copper of normal sheep from the Institute flock at Cambridge was studied over the period October-April for three lambing seasons and showed no changes characteristic of pregnancy; in contrast to the behaviour of human beings and possibly sheep of low copper status. What changes there were took place in both pregnant and nonpregnant sheep, did not reflect the transfer of copper to the foetus and appeared to be due to extrinsic factors.

Comparison of the blood copper of the lamb with that of its dam for four lambing seasons showed that it was a changing quantity at birth, being lower in the foetus, variable a few hours after birth and higher some days later than in the ewe.

The blood copper of suckling lambs was studied from birth in February-March until June, for three seasons. There tended to be high values in the first 1 or 2 weeks of life, which decreased in the course of approximately 10 weeks.

Respiratory activity of ejaculated bovine semen was studied in the presence of phosphate buffer (pH 7·4), egg-yolk medium or media containing different fractions isolated from the egg-yolk.

Seminal plasma from centrifuged bull semen has very little respiratory activity as compared with whole semen. The main factor affecting the respiratory activity of the semen is the concentration of active spermatozoa, but the respiratory activity is not directly proportional to the concentration of spermatozoa, since it falls off with reduction of concentration.

The copper, iron and lead contents were determined on an age series of foetal livers obtained during the latter half of pregnancy from normal ewes at Cambridge. The total amounts of the metals showed a rapid rise during the last 3 weeks of gestation due to an increase in the size of the organ and in the actual concentrations. Towards full term and in the new-born animal the results showed an increasing variation which even extended to twins. It is noted that foetal transference takes place without affecting the blood copper of the ewe or causing a physiological anaemia of pregnancy. The time at which the process is at its height is correlated with experience in the prophylaxis of swayback. It is estimated that the store of copper at birth may tide the lamb through the suckling period but the store of iron requires to be supplemented by the diet and that the ewe's milk may make a significant contribution towards this. The small amounts of lead found were of the same order as reported for normal humans and in swayback lambs in Derbyshire; hence the latter cannot be regarded as abnormal.

Kale silage was made in five large silos and the losses of dry matter and kale constituents determined.

The losses of dry matter averaged 33%, of N-free extract 41% and of crude protein 34%.

The percentage losses are higher than with wellmade grass silage, but, nevertheless, the yields of silage (and animal nutrients) per acre compare very favourably with those of other crops, including grass.

Inclusion of straw in kale silage did not reduce losses of dry matter; it merely reduced slightly the quantity of water lost.

The present communication deals with the results of an inquiry into the possibility of utilizing dried penicillin felt, a by-product of the manufacture of penicillin, in the feeding of livestock. The availability of this by-product on a suitable scale afforded an opportunity of obtaining information about the digestibility and biological value of a mould protein. During the course of the investigation, digestion trials with both sheep and pigs, and a farm-scale feeding trial with bacon pigs, have been carried out.