THE ORIGIN OF VARIATION 47 



from north to south is extraordinarily gradual, and except 

 when extreme forms are compared, it is only the averages that 

 differ. The comparisons must be made between individuals 

 occurring on the same line of longitude, the change occurring 

 more quickly in the east than in the west, the lines of equal 

 change probably corresponding with the summer isotherms, 

 which have a similar slope. Exceptions to this regularity are 

 found only in the Caucasus, where development of a special 

 geographical race of the Honey Bee introduces a fresh compli- 

 cation. Experiments on the effects of temperature are as yet 

 not very extensive, but they, like the seasonal changes observed 

 in Apis, show that cold produces artificially the same effects as 

 those found in nature. Nevertheless transportation experi- 

 ments have shown that the various naturally occurring types 

 are to a large extent hereditary. Alpatov's attempt to explain 

 his results is so characteristic of the orthodox way of dealing 

 with such facts, that it is worth setting out at some length. 



The possibility of the inheritance of a long-continued 

 environmental effect is dismissed ' because of the lack of any 

 credible experimental evidence of the inheritance of acquired 

 characters.' He goes on to attempt to show that the observed 

 characteristics of the southern forms may really be adaptive. 

 Thus ' the longer tongue of southern bees is probably con- 

 nected with the peculiarities of nectar secretion in the south 

 as compared with the more northern localities. Michailov 

 suggested that the longer tongue of southern bees is an adapta- 

 tion to dry conditions which lead to a lower level of nectar in 

 the south, and thus compel the bee to have a longer working 

 organ. We expressed the hypothesis that the southern bees 

 are obliged to have a longer tongue, not only because of a 

 lower nectar level, but also because of a probable difference 

 in the composition of the whole nectar-secreting flora. It 

 has been reported by many beekeepers that the southern, and 

 particularly the Caucasian, bees can fly longer distances 

 gathering nectar, and it is probable that in consequence their 

 wings are more developed and have a larger number of hooks. 

 The smaller size of the wax glands is probably connected with 

 the condition that the bees in the south have perhaps less 

 need to work upon the reinforcement of their nest. Hence 

 the difference in the tongues, the wings and the wax glands 

 (also probably in the first joint of the tarsus of the last pair of 



