184 Racial Studies in Fishes 



lations has not disappear'ed although the development took place under 

 the same circumstances. The result of our transplantation experiment 

 with Zoarces thus agrees with the experiment with Lebistes previously 

 described (see this Journal,Yo\. viii, pp. 150-153, 1919) and confirms the 

 conclusion that the difference, proved to exist between the two popu- 

 lations, is of hereditary (genotypical) nature. 



V. Comparison of Two Samples ok the same Population de- 

 veloped UNDER DIFFERENT ENVIRONMENTAL CONDITIONS. SlG- 

 NIB'ICANCE OF EXTERNAL FACTORS. 



The transplantation experiments just mentioned were continued in 

 1917 with material from Station 31. A great number of Zoarces indi- 

 viduals were in early summer, and therefore when the sexual organs were 

 still unripe, brought into four large wooden boxes placed in the same 

 embanked area near Station 31 as in 1916. 



When the experiment was brought to a conclusion the total number 

 of gravid females was 92. The number of offspring samples examined, 

 derived from transplanted specimens, was, including the 27 decades from 

 the 1916 experiment, altogether 119. 



The investigation showed that the average number of vertebrae 

 of the 119 decades was 114"535 + 0'493'. The corresponding figure 

 for the non- transplanted samples of the same population was in 1916 

 113101 ±0-447 and in 1917 113-251 ±0-372. It is therefore evident 

 that the external conditions, altered through the transplantation, have 

 decidedly raised the average number of vertebrae in the population. 



The same thing becomes apparent when the material is arranged in 

 another way. With the same arrangement of the material from the 

 transplantation experiment as was used in Table III, we arrive at the 

 following figures, each of which represents 100 individuals (10 decades) : 



1 For the sake of completeness it is stated that the average for the transplanted mothers 

 was 112*74 ±0'65, and for the males (111 specimens), found in the boxes at the conclusion 

 of the experiment, 112-95 ±0*61. 



