161 



Wilhelmi has stated that nearly all adults of S. calcitrans die in 

 winter, so that larvae and pupae are the hibernating forms, whilst many 

 adults of M . domestica survive. The numbers of 5. calcitrans noted 

 in the winter of 1916 and in the first half of 1917, however, militate 

 against an unrestricted acceptance of this view. 



M. domestica assumes an importance as a pest from April and May 

 to September and October, with its maximum in August. S. calcitrans 

 occurs from June and July to November and December and reaches 

 its maximum in September. This difference is important in connection 

 with investigations on the transmission of disease by flies. Apart 

 from unknown causes, it is probably due to unequal length of develop- 

 ment, if statements in the literature, especially by English workers, 

 are correct. Bodo von Bodemeyer has, however, observed no 

 difference in the time of development at 17-20° C. [62-6-68° F.]. 

 A low air temperature seems to check the development of S. calcitrans 

 more than that of M. domestica. This and the effect of light, food, 

 moisture and fermentation of manure still need investigation. The 

 effect of fermentation especially requires research, the data given 

 by Hewitt in 1908 and Roubaud [R.A.E., B, iii, 197] being con- 

 tradictory. 



It is remarkable that M. domestica decreases in September, whereas 

 5. calcitrans, though it seems more sensitive to cold, increases at that 

 time. The effect of Empnsa muscae in killing off the former may be 

 an explanation of this. 



Caullery (M.). Le Parasitisme et la Symbiose.— Par/s, Gaston Doin, 

 1922, 16mo, 400 pp., 53 figs. Price 14 francs, cloth. 



The matter dealt with in this volume formed the subject of the 

 author's lectures at the Sorbonne in 1919-20. 



Parasitism, from the point of view of general biology, is one of the 

 most significant manifestations of evolution, and has given rise to 

 definite types of organisms deeply modified by their specialised 

 conditions of life. It is not a condition that can be strictly defined, 

 being connected by an imperceptible transition with a looser associa- 

 tion, commensalism, on the one hand, and a closer one, symbiosis, 

 on the other. 



These general problems are discussed with the aid of concrete 

 examples, preferably such as have been the subject of recent research. 

 While more attention is devoted to parasitism in animals in its widest 

 sense, the main facts relating to this phenomenon in the vegetable 

 kingdom are also noticed. 



King (H. H.). The Englishman's Dog in the Tropics. — London, 

 The Field Press, Ltd., [1922] f'scap 8vo, 98 pp. Price 5s. 



This little book is full of information useful to dog owners in the 

 Tropics. 



The chapter on diseases includes notes on ticks, which carry tick 

 fever or canine piroplasmosis, fleas, jiggers, and the larvae of certain 

 flies. Ticks should be picked off every morning. If the dog's ears 

 are kept well covered with vaseline, these pests will not enter them ; 

 any found within can be killed by introducing vaseline, which clogs 

 the breathing pores. Fleas will not be troublesome if the dog's box 

 and blanket are kept clean. Dog soap is an effective remedy, but 

 frequent washings are bad for the coat. The jigger [Ttinga penetrans] 



