Febkuary 0, 1904.] 



SCIENCE. 



211 



other principles involved in radiate ' dis- 

 persal and the significance of these prin- 

 ciples in the interpretation of certain eco- 

 logical laws, habitats and faunal areas. 

 There are certain well-known physiological 

 laws which must be borne in mind. The 

 natural starting point is the vital optimum. 

 Departure from this optimum has a certain 

 definite result. The new vital conditions 

 are a cause of stimulation, and with further 

 departure (beyond a certain limit) lead to 

 increased stimulation or to unfavorable con- 

 ditions. This results in retarded growth, 

 development and reproduction of the or- 

 ganism as a whole. Thus the end results 

 of extreme departure from the optimum in 

 either direction are similar. In many re- 

 spects a center of geographic origin is an- 

 alogous to a vital optimum and any de- 

 parture from such a center may result in 

 effects similar to those brought about by a 

 departure from the vital optimum, retarded 

 growth, development and reproduction. 

 The results of extreme departures from 

 such a center are also remarkably similar. 

 In view of these relations, many apparently 

 isolated distributional and ecological facts 

 may be correlated. 



*A Feature in the Evolution of the Trot- 

 ting Horse: Francis E. Niphee, St. 

 Louis, Missouri. 



Twenty years ago the author published 

 an equation representing the relation be- 

 tween the speed of the trotting horse and 

 the time measured from any assumed date. 

 The date for the origin of any speed was 

 determined by the rate of increase in the 

 number of horses capable of making that 

 speed. It was, therefore, determined with- 

 out any reference to the date when some 

 individual horse broke the world's record. 

 The author drew the curve represented by 

 the equation published in 1882, and plotted 

 the observed cases from 1845 to date when 

 the record was actually broken upon the 



same diagram. The general agreement of 

 these experiments with the curve is very 

 striking. The points representing the ob- 

 served speed of record-breaking horses are 

 found to group themselves into steps cor- 

 responding to generations of the horse. 

 Flora Temple found the horse slow on the 

 computed speed represented by the curve. 

 She put the horse ahead. The same is true 

 of Dexter, of Goldsmith Maid, of Maud S. 

 and of Nancy Hanks. The diagram shows 

 that this evolution of speed is not a con- 

 tinuous operation, but that it goes on in 

 steps or jumps. In 1892 the new sulkj'' 

 with ball bearings made a similar jump in 

 the time of trotting a mile. It is very 

 likely that this advance will also be taken 

 up in time, and will correspond to less 

 radical improvements made in the old 

 sulky before 1892. A photograph of the 

 diagram was exhibited. On the same dia- 

 gram the performance of the running horse 

 is shown from three widely separated 

 records. 



Further Observations on the Breeding 

 Habits and on the Function of the Pearl 

 Organs in Several Species of Evento- 

 gnathi: Jacob Reighard, University of 

 Michigan. 



At the Washington meeting of the so- y^\j 

 ciety the writer described the breeding ' 



habits of the horned dace, stone-roller and 

 black-headed dace. In the breeding season 

 the males of these forms possess hard, 

 spine-like thickenings of the epidermis 

 known as pearl organs. The function of | 

 these transient structures had been hither- 

 to a matter of conjecture, but it was shown 

 that they are used by the males of some 

 species in their battles with one another 

 and in building their nests, while in the 

 males of all species the chief function of 

 the organs was shown to be that of en- 

 abling the male to hold the female during 

 the spawning act. In the present paper 



