284 THE VARIATION OF ANIMALS IN NATURE 



segments, and, as Hewitt says {I.e. p. 99), 'it is difficult to 

 imagine that the result is a mere coincidence of purposeless 

 variation.' But no exact differentiation of the species on 

 this basis is shown, and we must note, as Robson {I.e. p. 192) 

 pointed out, that these observations are rather of the nature 

 of casual field notes. 



3. Length of ovipositor in the cricket Gryllus {Lutz, igo8). 

 Following earlier observations of Uhler, Lutz measured 

 the length of the ovipositor in 200 female crickets from three 



1.2 13 J4 1.5 16 1.7 1.8 1.9 2p 2J 2.2 



Fig. 25. — Gryllus. Polygons of Frequency for Ratio 



of Ovipositor to Tegmina for Mainland ( ), 



Base of Spit ( ), and Apex of Spit ( ), 



at Cold Spring Harbour, New York. 



(Text-fig. 6 from Lutz, 1908.) 



stations on a spit projecting into Cold Spring Harbour. One 

 was from the sandy soil at the apex of the spit ; the second was 

 from the base, where there was some humus mixed with the 

 sand ; the third was from the ' mainland ' further inland, where 

 there was a considerable amount of humus. (The estima- 

 tion of the amount of sand and humus is loosely expressed.) 

 The ovipositors of the crickets from the apex were longer than 



