Architecture may seem an ambitious description to apply to the mass of observational data and conjecture which at present constitutes our knowledge of male sex behaviour, but it is well to keep in mind the existence of a complex integrated structure, genetic in origin but modified by environment, which determines the way an animal behaves in response to a given situation. The object of this paper is to suggest some of the ground plan of this structure. I have given a few references in the text, but wish to express my indebtedness in particular to the work of Beach (1948), Milovanov & Smirnov-Ugrumov (1940), and Gunn (1936), whose writings on the subject have been of such fundamental importance.

Opening the discussion on Dr. Walton's paper, Professor Wm. C. Miller (Animal Health Trust) said: “Dr. Walton has presented a paper which outlines the fundamentals of male sex behaviuor and forms an excellent skeletal strcuture into which the minutiae of behaviour can be fitted. I feel I ought to make an effort to fit some of the more precise details into their places and so contribute towards the presentation of a more complete idea of just what is involved in male sex behaviour. I am, however, inevitably faced with the limitations of available data and with the very great amount of variation in behaviour as between individuals, and even more between species of farm animals.

The very wide field of animal behaviour has no more fascinating application than in the bull stud of any artificial insemination centre where the male is subjected to close observation over a long period of time. After a year or two's experience one becomes aware of the qualifications expected of a bull if he is to become a successful A.I. sire. His general temperament must be good, he must be placid and easy to handle, be free from all vices, and be able to produce high quality semen as and when required, and at the same time he must possess superior genetical material so that there is hope of improved production from his progeny.

The paper by Mr. Smith, in which I have been greatly interested, is nevertheless outside my own particular field of study, which is gynaecology. Only in so far as I have carried out artificial insemination, using donated human semen, have I come in contact with a certain number of males in a somewhat comparable manner. I have also dealt with the seminal analyses of the husbands, because it is my practice to insist that the husbands of all subfertile patients should also be examined.

All female animals of spontaneously ovulating species show a pattern of behaviour at oestrus wrich differs from that of other times of the oestrous cycle, from the time before puberty and from that when the animal is senescent. This pattern is basically the same in all species but differs in detail from one to another. The matter which is of real interest concerning oestrous behaviour is its association with ovulation. This association is important with regard to the determination of the factors which control both oestrus and ovulation. It is also of immediate interest and importance in the domestic animals because fertility depends on the observation of oestrus, and the the relation thereto of ovulation and insemination.