SECTIONAL TRANSACTIONS— D. 333 



make it probable that this is also true of fertilisation in the Mammalia. 

 It was suggested by Adler that a lowering of the thyroxine content of the 

 circulation is the chief cause of the changes which occur in the vertebrate 

 at the onset of hibernation. This conclusion is supported by some experi- 

 ments on the excised heart of the frog. The temperature-pulse rate curve 

 of the heart of the winter frog is different in form from that of the summer 

 frog, and it has been found that the addition of thyroxine to the heart of 

 the winter frog produces a curve of the form typical of the heart of the 

 summer frog. None of several other endocrine substances has this effect. 

 Similar results have been obtained with the heart of the tortoise. Further 

 experiments which suggest that a similar rhythm in the amount or activity 

 of iodine compounds in the circulation plays a part in the production of the 

 somatic phenomena of diurnal sleep will be reported. 



Thus, these compounds have been found to be associated with changes 

 in the level of activity of animal tissues in several distinct phenomena. 

 It is suggested that this conclusion may be generally true, and that the 

 activity of animal cells is frequently controlled by the amount of these 

 substances present in them. 



Mr. C. Bryner Jones, C.B.E. — The origin and development of British cattle. 



Modern British cattle are of many breeds, each possessing some 

 characteristic — size, conformation or colour — that distinguishes it from 

 other breeds. While to the eyes of the cattle breeder these breeds, if 

 pure-bred, are so distinct as to be unmistakable for one another, to the 

 zoologist they are all the same thing in the sense that they are all referred to 

 one species . The diversity of breeds in the British Isles is remarkable , and to 

 the observer the question that at once suggests itself is, Where did they all 

 come from, and what was the primitive stock from which they derive their 

 origin ? 



The general opinion would seem to be that the domestication of cattle 

 belongs to the Middle Neolithic Period, and that the small short-horned ox, 

 known in this country as Bos lovgifrons and on the Continent generally as 

 Bos brachyceros, whose remains are found in Neolithic, as well as in later, 

 settlements, represents a domesticated race, which never existed, in Europe 

 at least, in the wild state and was already domesticated when it first made 

 its appearance on the European continent, having been brought hither by 

 migrants from Asia. With the westward trend of human migration, the 

 domesticated ox of Neolithic times was eventually brought by its owners 

 to Britain. The evidence of its Neolithic and later remains furnishes definite 

 proof of variability in which, by a process of selection governed by economic 

 and local conditions, the origin of the diversity of type to be seen in modern 

 British cattle may be found without having to fall back for explanation upon 

 outside influences — Roman, Germanic and Norman — to which historians 

 in the past would appear to have attached an undue importance. 



Afternoon. 



Dr. C. M. YoNGE. — The influence of the processes of feeding and digestion 

 upon evolution. 



The simultaneous study of morphology and physiology is essential for 

 the full understanding of the living animal. Evolution of function is as 

 important as evolution of structure. The evolution of animals is obviously 

 largely dependent on their ability to obtain and utilise food and to exploit 



