Chap. XVII. EVIL FROM INTERBREEDING. 107 



hardy birds : " so again, MM. Boitard and Corbie, 43 after forty-five 

 years' experience, recommend persons to cross their breeds for 

 amusement ; for, if they fail to make interesting birds, they will 

 succeed under an economical point of view, " as it is found that 

 mongrels are more fertile than pigeons of pure race." 



I will refer only to one other animal, namely, the Hive-bee, 

 because a distinguished entomologist has advanced this as a case 

 of inevitable close interbreeding. As the hive is tenanted by a 

 single female, it might have been thought that her male and 

 female offspring would always have bred together, more especially 

 as bees of different hives are hostile to each other ; a strange worker 

 being almost always attacked when trying to enter another hive. 

 But Mr. Tegetmeier has shown 44 that this instinct does not apply 

 to drones, which are permitted to enter any hive; so that there 

 is no a priori improbability of a queen receiving a foreign drone. 

 The fact of the union invariably and necessarily taking place 

 on the wing, during the queen's nuptial flight, seems to be a special 

 provision against continued interbreeding. However this may be, 

 experience has shown, since the introduction of the yellow-banded 

 Ligurian race into Germany and England, that bees freely cross: 

 Mr. Woodbury, who introduced Ligurian bees into Devonshire, 

 found during a single season that three stocks, at distances of from 

 one to two miles from his hives, were crossed by his drones. 

 In one case the Ligurian drones must have flown over the city 

 of Exeter, and over several intermediate hives. On another 

 occasion several common black queens were crossed by Ligurian 

 drones at a distance of from one to three and a half miles. 45 



Plants. 



When a single plant of a new species is introduced into any 

 country, if propagated by seed, many individuals will soon be 

 raised, so that if the proper insects be present there will be crossing. 

 With newly-introduced trees or other plants not propagated 

 by seed we are not here concerned. With old-established plants 

 it is an almost universal practice occasionally to make exchanges 

 of seed, by which means individuals which have been exposed 

 to different conditions of life, — and this, as we have seen with 

 animals, diminishes the evil from close interbreeding, — will 

 occasionally be introduced into each district. 



Witli respect to individuals belonging to the same sub-variety, 

 Gartner, whose accuracy and experience exceeded that of all other 

 observers, states 4G that he has many times observed good effects 

 from this step, especially with exotic genera, of which the fertility 

 is somewhat impaired, such as Passiflora, Lobelia, Fuchsia. 



43 ' Los Pigeons,' 1824, p. 35. pp. 39, 77, 158 ; and 1864, p. 206. 



44 ' Proc. Entomolog. Sue.,' Aug. 46 ' Beitr'age zur Kenntniss ae» 

 6th, 1860, p. 126. Befruchtung,' 1844, s. 366. 



*'* ' Journal of Horticulture,' 1861, 



