EVOLUTIONARY CHANGES 77 



Fritillaria (Figs. 48, 95, and) : 



F. ruthenica {n = ^) . .VVVVVI 



F. imperialis (n = 12) ) 



F. Meleagris (n = 12) >■ . V V II II II I 



and six other species ) 



F.pudica[n = iz) . . V II II II II I 



Acrididse (females) : 



Stenohothrus ) 



Chorthippiis I (n = 9) . . V V V I I I 



Chloealtis j (Figs. 25-28) f^ 



Other genera (;j = 12) . . II II II I I I 



Fig. 19. — Mitotic chromosomes from root-tips of Crocus species. A. 

 C. Aucheri, 2n = 6. B, the same in side view of early anaphase, 

 C, C. graveolens, 2n = 6. D, C. hyemalis, 2n = 6 + ^ff. E, C. aureus, 

 2n = 8. F, C. zonatus, 2n = 8. G, C, stellaris, 2n = 10. H, C. 

 Hueffelianus, 2n = 14. J, C. hadriaticus, 2n = 16. K, C. kardu- 

 chorum, 2n == 20. L, C. corsicus, 2n = 22. M, C. Imperati, 2n = 26. 

 X 3,700 (Mather, 1932). 



Note. — C is early metaphase with the limbs of the chromosomes 

 separate ; D is full metaphase with the limbs joined throughout their 

 length. In B, arrows indicate the position of the centromere at 

 which the daughter-chromosomes begin to separate. 



The direction of the changes suggested by this comparison 

 necessarily cannot be settled by direct evidence. But the fact 

 that the number 12 is constant in both the groups concerned, apart 

 from the types given here with other numbers, suggests that these 

 are derived from original forms with 12 chromosomes. Thus 

 F. ruthenica and Stenohothrus are derived from ancestral forms by 

 " fusion," F. pudica by " fragmentation." 



A comparison of Circotettix with other Tettigidae (Carothers, 1917, 

 1921 ; Helwig, 1929), of Nicotiana alata and N. Langsdorffii [n = 9, 



