October 5, 191 1] 



NATURE 



445 



ravages of which are nothing short of calamitous. In 

 1906 the loss in the Pfalz alone was estimated at six 

 millions of marks. After discussing the life-history 

 and habits, and the natural enemies of the caterpillars, 

 as well as a variety of chemical, mechanical, and 

 physical methods of dealing with the pest, the author 

 gives an interesting account of their infection with a 

 pathogenic mould, a species of Cordyceps. Ernst 

 Stromer takes us back to ancient days in his discussion 

 of the phylogeny of the Dipnoan stock, a subject raised 

 by his very interesting discovery of teeth of both 

 Protopterus and Lepidosiren in the Lower Oligocene 

 of Egypt. 



Plate's contribution to the Festschrift is an expanded 

 version of the inaugural lecture which he gave in 

 entering upon his duties as professor of zoology in 

 Jena. He deals with the laws of inheritance in their 

 relation to general evolution-theory. He has been 

 breeding mice and has found not a single fact against 

 the Mendelian theory. But he does not think that the 

 selection theory has lost any of its importance. Some 

 of his analyses of current conceptions are very inter- 

 esting; thus he distinguishes seven forms of germinal 

 variation, five kinds of atavism, and several kinds of 

 correlation. 



The third volume begins with observations by 

 Arnold Lang on the heart-beats of hibernating snails. 

 As the temperature falls the beats become fewer and 

 fewer, but even at — 3 C. they were still observed. A 

 heart that can beat fifty times a minute in summer 

 may only beat 236 times a minute at a temperature 

 of 2'65° C. in February. In the next study Karl von 

 Frisch takes us out to brooks and streams, and in- 

 quires into the colour-change of the trout and the 

 minnow. It is many years since Pouchet demonstrated 

 the importance of the sympathetic system in this con- 

 nection, but von Frisch has already in this " vorlaiifige 

 Mitteilung " got further into the business. He has 

 shown that there is in the anterior end of the medulla 

 oblongata a special centre, the stimulation of which 

 Bakes the fish lighter, i.e. makes the chromatophores 

 contract. He has also found the place where the 

 nerve-fibres that control the chromatophores pass out 

 of the spinal cord into the sympathetic, in which they 

 extend forwards and backwards. 



By means of ingenious experiments, especially on 

 bicephalous Planarians, Paul Steinmann has shown, 

 for Triclads, that the nature of what is regenerated, 

 e.g. w-hether a head or a tail, depends, not on the line 

 of cutting, nor on the adjacent tissue, but on the 

 regenerating organism as a whole. Even distant parts 

 of the regenerant have their "organising" influence 

 on the regenerate. Another paper dealing with re- 

 generation is by Gustav Wolff, who reports on the 

 continuation of his studies on newts. He has pre- 

 viously shown that the regeneration of the lens takes 

 place apart from nervous stimulus, but now he shows 

 ithat in the regeneration of the hind limb a nervous 

 factor is indisputable. He makes much, for instance, 

 of the remarkable fact that when an abnormal limb, 

 say one with only two toes, is cut off, the regenerated 

 limb has also only two toes. There is a very inter- 

 esting historical reference to a forgotten paper by 

 NO. 2l88, VOL. 87] 



T. J. Todd, who directed attention, in 1823, to the 

 influence of the nerve in the regeneration of the 

 newt's leg. 



An investigation of a very different type is that of 

 W. F. Ewald on the contraction of the adductors in 

 freshwater mussels. He has discovered a special 

 " tonus-current," and gives a definition of the "tonic 

 muscle-contraction." It is not oscillatory or discon- 

 tinuous, but a persistent process, both in its mechanical 

 and its electrical aspects. Albrecht Bethe deals with 

 the equilibration of aquatic animals, discussing those 

 with statocysts and those without, those the construc- 

 tion of which gives them an automatic stability, and 

 those "labile" forms that keep themselves in a par- 

 ticular position by a coordination of movements. In 

 some young fishes there is at first an automatic deter- 

 mination of the position, and the coordination is sub- 

 sequently acquired. O. Maas has studied the peculiar 

 involution-processes which occur in various sponges 

 when they are starved or kept without sufficient lime 

 salts. By passing into a resting stage, comparable to 

 gemmules, the sponge may survive the disadvan- 

 tageous conditions and exhibit subsequent revivifica- 

 tion. One of the interesting general results is the 

 corroboration of the view that sponges are essentially 

 diploblastic. Th. Boveri has studied the develop- 

 mental potencies of Ascaris-blastomeres in cases where 

 the normal type of cleavage has been departed from, 

 either as the result of double fertilisation or in conse- 

 quence of centrifugal rotation. He gives the coup de 

 grdce to the hypothesis of differential nuclear division. 



F. Doflein takes us into the open-air again with 

 his very interesting — though admittedly preliminary — 

 study of the behaviour of two prawns, species of 

 Leander, common on the Riviera coast. He discusses 

 their fine coloration and its changes ; the different 

 kinds of chromatophores and pigments, red, blue, 

 yellow, and white ; their behaviour when feeding, 

 when cleaning themselves, and so on ; and the re- 

 actions to diverse stimuli. 



This remarkable tribute, a credit alike to the genial 

 professor and his school, ends with an interesting 

 study of the awakening of the hibernating hedgehog. 

 Whether automatically, or by " pulling itself to- 

 gether," the hedgehog warms itself up, and that 

 rapidly. The chemistry of this, according to Tanzo 

 Yoshida and Ernst Weinland, is that a rapid combus- 

 tion of glycogen occurs, and that fat serves as an 

 accessory fuel to the vital fire. 



THE AGRICULTURAL DEVELOPMENT OF 

 EGYPT. 



Text-book of Egyptian Agriculture. Edited by G. P. 

 Foaden and F. Fletcher. Vol. ii. Pp. viii + 321- 

 878. (Cairo : National Printing Department, 1910.) 

 Price 9s. 



IN the agricultural development of a country two 

 lines of attack have always to be followed : in- 

 vestigations are made with the objects of discovering 

 the best crops to grow and the best methods to 

 follow ; and the cultivator — who is generally constitu- 

 tionally conservative — has to be persuaded that the 



