JOIIS. SOHMIDT 151 



Thf 8pecinu«n» oiiiploytMl in the fX|MTiiiH*nt.s were H('I<-ct4'(l from two 

 racfj* with w-hich sincf 1915 srh»ctinn rx|MTiiiirnU \\iu\ hvm umlrrUikcn, 

 pjirtly U»wiinls a hi^h. jNirtly towanlH a low duiiiIkt of doi-Hal rays. 

 The jwrentsH had. roHiHTtivoly. both H and hoth (J rays in tho dornjil Hn. 

 In i»ach case the spi'ciniens were kept at a constant t<'ni|H'mtun', viz. 25 . 

 In addition, in «»rder U) srcurc uniform environment, the H|H-eimen« 

 whoiw offspring should In* comj)ared were placed in the same a<|uarium, 

 sejmnittHl only by a trelliswork of thin ^lass tubes. In other wohJh 

 they livinl in ijuite the same body of w.iter, maintained at a constant 

 temperature. The aipiarium contjiined no plants, l)ut a continuous 

 stream of atmospheric air bubbled through the water. 



The exjKTiment falls inti> two series, A and B. In scries A there 

 were employed partly (^ 2G9 and J 270 (ejich with (i rays), partly (/ 2()7 

 and J 2G8 (each with 8 mys). For series B there were employed jwirtly 

 </" 27-t and ? 27.S (each with (5 rays), partly ^ 27G and ? 275 (each 

 with 8 rays). All the exjx*rimental fish in series A were kept in the 

 same aquarium which stood at the side of the one in which all the fishes 

 belonging to series B were placed. 



From the appended Table VII and from the graph on p. 152 one 

 remarks that there wtis in both series a very great difference in the 



TABLE VII. 



Nunther of dorsal rays in offsprimj of four differeyit pairs of parents 

 at a constant temperature of 25° C. 



average number of rays in the offspring of fishes with () anfl with 8 rays, 

 namely in the first series 1"131 (Probable error of ditierencr = 004.')) 

 and in the second 1-241 (RE. Diff. = 0045). 



This difference cannot be due to difference in environment because 

 the fishes swam in the same aquarium, indeed in the very s^ime water 



