206 THE MINUTE ANATOMISTS 



Leeuwenhoek had his own remarks to oflfer, sometimes 

 "well-founded, sometimes not. He showed that repeated 

 inverted images are formed by the corneal facets, but 

 that we need not suppose each image to be separately per- 

 ceived ; we do not see double because we have two eyes. 

 He throws out the bold speculation that the hexagonal 

 cells of the honeycomb are due to an impression received 

 from the hexagonal facets of the bee's eye, a supposition 

 which Swammerdam gravely refuted.^ As a proof of the 

 quickness of sight which may be conferred by a com- 

 pound eye, he relates how he watched a swallow chasing 

 a dragon-fly over the surface of a large pond, and how 

 the swallow was baffled by the speed and unexpected 

 turns of the insect, which kept it always several feet in 

 front of the enemy. Leeuwenhoek points out that com- 

 pound eyes are not peculiar to insects, but occur in 

 crustaceans also. 



Viviparous Reproduction by Unfertilised Aphids^ 



Leeuwenhoek remarked that expanding buds of 

 currants, cherries and peaches were sometimes distorted, 

 and the unexpanded leaves crumpled. On close ex- 

 amination he found that the affected buds were beset by 

 aphids or plant- lice. Intending to investigate their 

 life-history, he sought for eggs, but could find none. 

 When he opened the bodies of the aphids, he found to his 

 surprise no eggs but young aphids, resembling the 

 parent in all but size. An aphid no more than a fort- 

 night old might contain as many as sixty young ones, 

 so that propagation went on with extraordinary rapidity. 

 The birth of the young was observed. No males were 



1 Biblia Naturae, p. 490, and supra, p. 188. 



2Epist. 90, Arc. Nat. (1695) ; Epiat. 94, Cont. Arc. Nat. (1695) ; Epiat. 104, 

 Cont. Arc. Nat. (1696) ; Epist. 134, Ep. Soc. R. (1700). Vol. II, pp. 486-502 ; 

 2nd pagination, pp. 9-11, 148-156 ; Vol. Ill, 263-280. 



