128 



THE BRITISH NATURALIST. 



[June 



pour devenir d'un blanc de lait, mais parfois anosi elle se reproduit 

 de couleur aussi vive." A yellow example mated with one of the 

 ordinary colour, the young were some yellow, others blackish, but 

 later all became of the latter colour. Two yellow individuals having 

 mated, the colour of the young differed, some were blackish-yellow, 

 "jaune noiratre,*' others yellowish-white, ''jaune blanchatre," the 

 colour in both cases gradually becoming brighter, "peu a peu plus 

 vive." The vsiV. sinistroysa M. Collin found in considerable numbers 

 in the years 1871 and 1872, in the first year the greater number of 

 individuals were adults, in the second year a large proportion were 

 fragile and more slender, these facts leading the writer to the 

 conclusion that there were two generations. Those placed in the 

 aquarium produced sinistral young. The author points out the 

 impossibility of a union between individuals of the dextral. and sinistral 

 forms, and concludes his remarks on this variety as follows : " 11 est 

 done de fait acquis que la variete senestre est hereditaire et se 

 maintient." The variety lua.xiina, 8 cm. (above three inches) in length, 

 when placed in the aquarium produced the progeny much smaller than 

 the parents, still smaller in following years, till the var. aquarii, 

 16 mm. was finally produced; but the race was produced in the natural 

 habitat, "Ce milieu ne changeant pas, la variete devint hereditaire." 

 These facts appear to me to prove that size depends on environment. 

 Before leaving this most interesting paper I will quote one more 

 sentence showing the author's opinion of the permanence of varieties 

 under suitable conditions. " Lorsque deux Limn^es de vari6t6 

 semblable, quelqu'eloign6-e qu'elle soit du type, s'accouplent et vivant 

 dans des conditions identiques a celles dans lesquelles elles sont nees 

 et ont vecu elles-memes, la variete de form ou de couleur de I'animal 

 ou de la coquillc persistera chez les petits." — W. A. Gain, Tuxford. 



Errata. — Page 105, between last and preceding line insert 

 "mysterious characteristics of this." 



NATURALISTS OF THE DAY. 



v.— J. W. DOUGLAS, F.E.S. 



John William Douglas was born on i5tli of November, 1014, and 

 is therefore nearly 7S years of age. r rtjni his early days, being ;i 

 lover of nature, he was intended lor a botanist, and was taught } 

 accordingly, but when he was 20 years of old he received an \ 



