ON VARIETIES, RACES, SUB-SPECIES, AND SPECIES. 73 



of the species to which they belong. To species in this condition 

 we shall give the name of Alpha. 



We distinguish several sorts of differences too sliglit to con- 

 stitute varieties to which a special name can be given. 



The first sort is the variatio7i of botanists, which is not con- 

 stantly reproduced by generation. 



The second sort is the difference of size and vigour of indi- 

 viduals arising from their development in favourable or unfavour- 

 able circumstances ; although these differences may be trans- 

 mitted from parents to their ofispring Avhere the circumstances 

 are the same, yet as they disappear under other circumstances, 

 they are too unimportant to entitle the individuals in which they 

 are found to distinct names. 



In short, after having pointed out the characters common to 

 well developed individuals of a species, it is sufficient to take 

 notice of the variable qualities or variations, and the circum- 

 stances capable of producing some modification of size or vigour 

 in the individuals. 



Kffilreuteria affords an example of a species to which Alpha 

 is applicable. 



Common rye {Secale cereale) may, according to M. Loiseleur- 

 Deslongchamps, be given as a second example ; for it is generally 

 supposed by botanists and agriculturists to have undergone no 

 permanent modification, notwithstanding the long time it has 

 been in cultivation, and the great diversity of soil and climate in 

 wliich it has been reproduced in endless succession ; the only 

 change that has been observed in it is a dimiimtion of size and 

 vigour in poor ground. It was sufficient for Tessier to sow 

 several times in autumn in the same place petit rye, tremois rye, 

 marsais rye, and spriny rye, to ^ai a plant identical with com- 

 mon rye. 



According to M. Agassiz, the pike (JEsox lucius) and perch 

 {Perca fiuviatilis) are similar examples in the animal kingdom. 



In short, in the species to which the distinction Alpha is 

 applicable, every well-developed individual may be taken as the 

 type. 



Distinction Beta. 



This will not be so if a certain number of individuals belong- 

 ing to the same species present, under certain circumstances, any 

 remarkable and constant differences. Such is the case witli the 

 variety spectabilis of Robinia pseud-acacia : the spiny indi- 

 viduals represent the species, and the spineless individuals 

 represent a variety of the same species, which variety cannot, as 

 already stated, be propagated from seed. 



The origin of this variety being perfectly known, we cannot 



