18 

 Reviews of recently publisFied textbooks on Embryology 



GENERAL 



The "Methuen's monographs on biological subjects" are a somewhat more 

 luxurious form of pocketbook edition than the German "Sammlung Goschen" 

 booklets. They have been printed in a more convenient letter type and on better 

 paper and have been bound in a nice band. This is of cour.se reflected in the 

 price, varying between 6 and 10 shillings, which is about 1 j/2 to 2 times the 

 price of the German edition. There are, however, other interesting differences 

 between the two forms of publication. Whereas the German edition gives more 

 the general survey of the well established knowledge in the field concerned, 

 the English edition actually offers us the up to date progress in the various 

 problems with a very extensive bibliography. It is more particularly written 

 for scientists and students and less for teachers and laymen interested in the 

 field, for which latter group the German edition will be more welcome. The 

 German edition is therefore also much more richly illustrated than the English 

 monographs. 



P. D. NIEUWKOOP 



"VERTEBRATE SEXUAL CYCLES" 

 1951 

 by W. S. Bullough Methuen & Co. Ltd., London 



117 pp. with 12 illustrations John Wiley & Sons, Inc., 



New York 

 Price: 6 s. 



The very extensive literature on the sexual physiology of the Vertebrates is 

 briefly summarised in this booklet, indicating the main facts and theories with 

 many references in order to enable the reader to extend his reading to the 

 original literature. In this booklet the factors determining, controlling or affect- 

 ing the seasonal and the oestrous reproductive cycles of the vertebrates are 

 discussed. They can be divided into ultimate and proximate factors. In the 

 ultimate factors the food supply is probably the most important. For their 

 genetical fixation natural selection has been responsible. The proximate causes 

 would be the internal reproductive rhythm, the environmental changes in light 

 and climate and finally that group of factors in the immediate environment of 

 the individual animal as breeding area, social grouping etc. The very extensive 

 field of hormonal regulations has been only very briefly surveyed, after which 

 the last chapter has been devoted to sexual behaviour, which subject has also 

 been treated in outlines. 



This booklet which has been written in a clear and stimulating style and in 

 which the essential aspects have been stressed and details have been omitted 

 as much as possible, offers a very good summary of this interesting problem. 

 We therefore highly recommend it to zoologists, medical and veterinary scien- 

 tists and students. 



P. D. NIEUWKOOP 



