ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 295 



areas as the black does to the more heavily pigmented areas of the wild 

 species ; and it is a highly interesting fact that the nigrescent sport 

 throws back to the type of pattern characteristic of a parent form. 

 Tan is merely one of the shades of that class of colour which is called 

 " erythristic," and it appears that albinism, erythrism, and melanism 

 are three consecutive stages in colour-variation, erythrism being the 

 incipient stage either of albinism or melanism. 



Law of Fatigue in Racing.* — A. E. Kenelly finds from the records 

 of trotting, racing, and running horses, as well as from those of run- 

 ning, walking, rowing, skating, and swimming men, that the time varies 

 approximately as the ninth power of the eighth root of the distance. 

 DoubUng the distance means increasing the time 118 p.c. The time 

 occupied in a record -ma king race varies approximately inversely as the 

 ninth power of the speed over the course. Doubling the speed cuts, 

 down the racing time 512 times. The distance covered increases 

 approximately as the eighth power of the ninth root of the time. 

 Doubling the time of the race allows of increasing the course length 

 by S5 p.c. The distance covered increases approximately as the inverse 

 eighth power of the speed over the course. Doubling the speed cuts 

 down the distance that can be covered 256 times. The speed over the 

 course varies approximately as the inverse eighth root of the distance. 

 Doubling the distance brings down the speed about 9 • 3 p.c. The speed 

 over the course varies approximately as the ninth root of the racing time. 

 All these statements are different aspects of one and the same fact. 



" If any of the three quahties, L, T, and V ( = - ), be plotted on 



logarithm paper as ordinates to either of the other qualities as abscissae, 

 the record points will fall on, or near to, a straight line." 



" Athletes aspiring to break racing records might succeed better in 

 attacking those whose points fall below the straight lines of speed against 

 distance, or above the straight lines of time against distance, rather than 

 those whose points fall on tlie opposite sides of those lines." 



With the exception of bicycling, the law of fatigue in racing is the 

 same or very nearly the same for horses and for men. 



Habits of Fierasfer affinis.f — E. Linton gives an interesting account 

 of the behaviour of this Fierasfer when forced to leave the body of its 

 host, Stichopus mmbii. When the Holothurian is kept for a short time 

 under a finger-bowl so as to produce partial asphyxiation, Fierasfer 

 leaves the body of its associate and swims excitedly near the surface of 

 the water, taking in gulps of air. Its sense of sight appeared defective, 

 but this was not proved. Apparently by accident it touches the body of 

 the Holothurian with its snout ; immediately it feels its way backward to 

 the posterior end without pause or regression, as if following a scent. 

 Instantly on touching the cloacal opening, the slender tail is brought 

 round with a very rapid whip-like movement, which terminates in a 

 thrust whereby the tip is inserted. Up to this point the fish is excited ; 

 it now leisurely insinuates its body into the host. 



* Proc. Amer. Acad., xlii. (1906) pp. 275-331 (18 tables), 

 t Amer. Naturalist, xli. (1907) pp. 1-4 (2 figs.) 



