ADDIIKSS. 9 



researcli, and it is not going too far to say that there is not a single 

 species which would not amply repay the devotion of a lifetime. 



One remarkable feature in the modern progress of biological science 

 has been the application of improved methods of observation and experi- 

 ment; and the employment in physiological research of the exact mea- 

 Burements employed by the experimental physicist. Our microscopes 

 have been greatly improved : achi-omatic object-glasses were introduced 

 by Lister in 1829 ; the binocular arrangement by Wenham in 185G ; while 

 immersion lenses, first suggested by Amici, and since carried out under 

 the formula of Abbe, are most valuable. The use of chemical re-agents 

 in microscopical investigations has proved most instructive, and another 

 very important method of investigation has been the power of obtaining 

 very thin slices by imbedding the object to be examined in paraffin or 

 some other soft substance. In this manner we can now obtain, say, fifty 

 separate sections of the egg of a beetle, or the brain of a bee. 



At the close of the last century, Sprengel published a most suggestive 

 work on flowers, in which he pointed out the curious relation existing 

 between these and insects, and showed that the latter carry the pollen 

 from flower to flower. His observations, however, attracted little notice 

 until Darwin called attention to the subject in 1862. It had long 

 been known that the cowslip and primrose exist under two forms, about 

 equally numerous, and diSering- from one another in the ari-angements of 

 their stamens and pistils ; the one form having the stamens on the summit 

 of the flower and the stigma half-way down ; while in the other the rela- 

 tive positions are reversed, the stigma being at the summit of the tube 

 and the stamens half-way down. This difference had, however, been re- 

 garded as a case of mere variability ; but Darwin showed it to be a 

 beautiful provision, the result of which is that insects fertilise each flower 

 with pollen brought from a different plant ; and he proved that flowers 

 fertilised with pollen from the other form yield more seed than if fer- 

 tilised with pollen of the same form, even if taken from a diSerent plant. 



Attention having been thus directed to the question an astonish- 

 ing variety of most beautiful contrivances has been observed and de- 

 scribed by many botanists, especially Hooker, Axel, Delpino, Hildebrand, 

 Bennett, Fritz Miiller, and above all Hermann Miiller and Darwin 

 himself. The general result is that to insects, and especially to bees, we 

 owe the beauty of our gardens, the sweetness of our fields. To their 

 beneficent, though unconscious action, flowers owe their scent and color, 

 their honey — nay, in many cases, even their form. Their present shape 

 and varied arrangements, their brilliant colors, their honey, and their 

 sweet scent are all due to the selection exercised by insects. 



In these cases the relation between plants and insects is one of mutual 

 advantage. In many species, however, plants present ns with complex 

 arrangements adapted to protect them from insects ; such, for instance, 

 are in many cases the resinous glands which render leaves unpalatable ; 

 the thickets of hairs and other precautions which prevent flowers from 



