4S6 



NATURE 



[June 23, 1910 



Although the essential similarity of light and radiant 

 heat is insisted upon, and the distinction between 

 heat and radiant heat clearly drawn, no experiments 

 to illustrate the application of the laws of reflection 

 to the latter are given. The experiment with two 

 concave mirrors in which heat is transferred by radia- 

 tion from one focus to the other is surely one of the 

 best for impressing on students the connection between 

 the various radiations. 



(3) This much longer volume is not nearly so good 

 as those just commented upon. It is written specific- 

 ally for the London matriculation examination, and 

 it may be said at once that it is much too difficult. 

 It would have been better if less material had been 

 treated more fully. As it is, the book is overcrowded 

 with statements which it would be impossible for the 

 elementary student to deduce for himself — he must 

 merely commit them to memory. He is told, for in- 

 stance, that the "dyne" is the weight of one gram 

 divided by g8i, a statement which is not only in- 

 correct, but conveys no impression of the importance 

 of the absolute unit of force. A long discussion is 

 entered upon as to the relative merits of the two-fluid 

 and one-fluid theories of electricity. The matricula- 

 tion student is advised in the text to accept the one- 

 fluid theory, and then a footnote tells him that prob- 

 ably he will have to revert to the two-fluid theory 

 because recent experiments point to the existence of 

 positive electricity. Controversies of this kind are 

 altogether out of place in elementarj' text-books ; they 

 only confuse the student. 



There is a profusion of examples at the end of each 

 chapter. These are, as a whole, good ; but it is doubt- 

 ful whether the pupil would be in a position to answer 

 them intelligently if left to himself. 



OVR BOOK SHELF. 



Studien iiber die Bestimmting des iveiblichen Gesch- 

 lechtes. By Prof. Achille Russo. Pp. v + 105. 

 (Jena : Gustav Fischer, 1909.) Price 3 marks. 

 PI^o . Russo has published a general account of very 

 interesting experiments which he has made on the 

 determination of the female sex in rabbits. His 

 method was to dose the animals with lecithin — a well- 

 known constituent of yolk of egg — administering it 

 in various wavs. He injected it into the peritoneal 

 cavity or subcutaneously ; he even introduced it 

 through the mouth. From control experiments it 

 seemed clear that one of the results of introducing the 

 lecithin in considerable quantity into the system, 

 where it normally occurs in many difTerent tissues, 

 was the accumulation of deutoplasmic material in the 

 ov-'. i'-^n follicles and in the oocytes; and Russo 

 found that rabbits treated in this way, and subse- 

 quently mated, had more female than male offspring. 

 Sometimes all the offspring were female. The 

 security of the conclusion that the lecithin treatment 

 was the condition of this disproportionate number of 

 female offspring depends on the number of cases 

 investigated and on the avoidance of selected stocks. 

 Russo is well aware of this, and he does not betray 

 any dogmatism. 



In the normal ovary, or in what he believes to be 

 the normal ovary. Prof. Russo distinguishes two 

 kinds of ova, one kind rich in nutritive material 

 deposited in the zona pellucida and in the vitellus, 

 the other kind with little or none. The lecithin 



NO. 2 12 I, VOL. S^] 



treatment increases the number of the richly equipped, 

 highly anabolic ova, and they are (if the correlation 

 has been adequately substantiated) the female-pro- 

 ducing ova. 



In young rabbits of five or six months the ova 

 show little vitelline material, no chromidial cor- 

 puscles, and a clear zona pellucida. This is a sign 

 of deficient nutrition, and there is some evidence that 

 these very young ova tend to be male-producing. As 

 the nutrition of the ovary improves with age, the ova 

 become better equipped with " embryoplasmic " 

 material, and tend to be female-producing. The 

 general result of Prof. Russo's interesting experi- 

 ments is to show that the ovary is a very plastic 

 organ, responding to the lecithin treatment by an 

 increase in the number of female-producing ova. He 

 suggests that the lecithin treatment of males may 

 afTect the spermatozoa in an analogous way — in their 

 mitochondrial apparatus. In developing his thesis, 

 the author communicates many .v'aluable observations 

 on the germinal epithelium, the granulosa, the zona 

 pellucida, and the various chromatic substances which 

 appear in the ooplasm. Statistics of the experiments 

 and details as to methods emploved are duly sub- 

 mitted, and the whole discussion is conducted in an 

 admirable scientific temper. 



Report on the Mines and Mineral Resources oj Natal 

 (other than Coal). By Dr. F. H. Hatch. Pp. 

 xii+155 + vii plates. Published by order of the 

 Natal Government. (London : Printed by R. Clay 

 and Sons, Ltd., 1910.) 

 This little volume, which contains the results of an 

 eight months' prospecting trip in the colony of Natal, 

 undertaken by Dr. Hatch on behalf of the Natal 

 Government, is extremely disappointing, as the only 

 conclusion that can be drawn from it is that Natal 

 possesses no mineral, other than coal, that is deserv- 

 ing of any serious attention. Dr. Hatch sums up his 

 impression in the words, "no large well-developed 

 metal mines, either of the precious or of base metals, 

 exist in Natal." To which may be added that the 

 report indicates that no deposit has yet been met with 

 which promises to be worth developing or to be 

 likely to be mined with any measure of success, and 

 the same is true of the non-metallic deposits — coai, 

 of course, being always excepted. Deposits of gold, 

 copper, tin, iron, manganese, chromium, lead and 

 silver, molybdenum, of limestone, phosphate, graphite, 

 asbestos, gypsum, salt, nitrate, oilshale and petro- 

 leum, building stone, slate, clay, &c., are known to 

 exist and have here been reported on, but nothing of 

 commercial value seems to have been met with any- 

 where. The value of the mineral output of Natal for 

 1908 is given as 741,158/., out of which the value of 

 the coal is 737,169/. Further comment is needless. 



Modelling from Nature. A New and Original Methodl 

 of Clay Modelling. By Lilian Carter. Pp. 32 ; andl 

 16 plates of models copied from nature. (London :| 

 Cassell and Co., Ltd., n.d.) Price js. 6d. net. 

 Though we are sceptical as to the newness an^J 

 originality of Miss Carter's method of teaching cla 

 modelling, there is no doubt that work of the kir 

 she describes interests young children, and assists 

 making them accurate and alert in examining natur^ 

 objects, as well as deft with their fingers. 



The Time of the Singing of Birds. Pp. 12C 



(London : Henry Frowde, 19 10.) Price 35. 6d. netll 

 This anthology of verse will appeal to all bird-l overs.! 

 Three compilers have been able, with the cooperatic" 

 of authors and publishers, to bring together a cham 

 ing collection of modern poems, as well as the bettc 

 known older verses dealing with bird life. 



