174 SCIENCE PROGRESS 



substance which requires to be released in some way or other before it can have 

 any effect. It is stated on p. 125 that only among myxinoids is normal 

 hermaphroditism met with in vertebrata. This is not strictly accurate, for in the 

 Bufonidae (Toads) the males possess a rudimentary ovary, Bidder's organ, which 

 may be as large as the testis, although probably not functional. Throughout the 

 whole of the Urodela and Anura some degree of hermaphroditism is by no means 

 uncommon : ova may be developed in the substance of the testis, or one testis may 

 be replaced by an ovary : and more or less well-developed oviducts are often 

 met with in male Amphibia. These facts suggest that the balance between the 

 tendencies to make the individual male or female in this group is fairly even and 

 readily upset — a possibility further borne out by Hertwig's experiment wherein 

 " indifferent " individuals were produced, and one that makes it impossible to 

 press too far the application of the results obtained in this class to other classes 

 of vertebrates. 



The author concludes that " Sex is dependent on a physiological condition of 

 the organism, a condition depending on the interaction of certain chromosomes 

 with the protoplasm of the cells, and therefore determined, in the absence of other 

 disturbing factors, by the presence or absence of these particular chromosomes." 

 Before any advance is made on this, much work will have to be done, work that 

 will doubtless be stimulated by Dr. Doncaster's well-arranged, thoughtful pages. 



C. H. O'D. 



Nerves. By David Fraser Harris, M.D., CM., B.Sc, etc. [Pp. x + 256, 

 with 8 figures.] (London : Williams & Norgate, 191 5. Price is. net.) 



The Home University Library has already produced a number of good books 

 in which specialists have set out in non-technical language the salient facts and 

 theories of their subjects. The present volume is a worthy addition to the series 

 and in it the functions of nerves and of the nervous system and the parts they play 

 in the ordinary activities are dealt with in a clear and readable manner. Slips 

 have crept into the early chapters here and there. On p. 12 we read that "there 

 is no neural socialism," a quite meaningless phrase that is intended to suggest 

 that the various nerve cells are functionally differentiated. As an example of a 

 reflex action it is stated that if a frog has its brain destroyed it will still change 

 its skin colour in response to differences in the intensities of the light reaching 

 the eye. If this be a fact, then it is not a reflex action, as that part of the reflex 

 arc intervening between the optic nerve and the cutaneous nerve would have been 

 destroyed with the brain. On p. 107 it is stated that " Instincts are inherited 

 habits." This is supported by no evidence whatever, and is a statement that has 

 long since been discredited. 



The last chapters are interesting and the book as a whole is well worth 

 reading. 



C. H. O'D. 



BOTANY 



Practical Field Botany. By A. R. Horwood, F.L.S. [Pp. xv + 193, with 

 20 plates and 26 other illustrations.] (London: Charles Griffin & Co., 1914. 

 Price 5.?. net.) 



ONE hardly knows in what category to place this book. The author is obviously, 

 sincerely, and earnestly anxious to foster interest in the study of plants, and has 

 apparently written this book in a great hurry. He has much to say about " the 



