4 VII. INTERNATIONAL ZOOLOGICAL CONGRESS 



rounded secondary lobe vs. no rounded secondary. In the usual 

 manner of designating gametic formulae, B. bp. heteris will be repre- 

 sented as AB, possessing both dominant characteristics; rhomboidea 

 will be aB ; tennis, Ab, and simplex, ab. From this it will be inferred 

 that heteris is dominant over all of the other forms; that rhomboidea 

 and tennis are both dominant over simplex, and recessive to heteris; 

 and that when tennis and rhomboidea are crossed together, and when 

 heteris and obtusa are crossed together, heteris appears as the F 1? and 

 all four forms will occur in F 2 in the ratio 9:3:3:1. All of these in- 

 ferences have received complete experimental confirmation. 



Now, in the cross between B. bursa-pastoris and B. heegeri it is 

 important to note that B. heegeri has a rosette possessing the two 

 dominant characteristics of B. bp. heteris, though the primary lobe, 

 A, is usually wider and more blunt than the best developed examples 

 of the B. bp. heteris type, and the rounded secondary, B, is rendered 

 less prominent because of the lesser depth of the sinus which sets it 

 off from the primary lobe. Reciprocal crosses were made between B. 

 heegeri and B. bp. simplex. The F x hybrids were essentially uniform, 

 and were of the heteris type, though somewhat stunted because of 

 unfavorable conditions in the propagating-house during the period of 

 their development. All had the flat, triangular capsules of Bursa 

 bursa-pastoris. In F 2 there appeared the four forms of rosette already 

 described, in combination with each type of capsule. The rosettes 

 presented many instances of the best developed examples of the four 

 described forms, particularly interesting being the fact that much 

 better developed heteris rosettes occur in the F 2 than are seen in pure- 

 bred B. heegeri, though these heteris characteristics must have come 

 directly from the heegeri side of the cross. The numerical results of 

 these crosses may be tabulated thus : 



Fed. No. 

 06196 

 06197 

 06212 



Bursa bp. simplex (abC) X Bursa h. heteris (ABc) 



Fed. No. 056.64 



Bursa bp. heteris (ABC) 



Fed. No. 059. 



Bursa-pastoris series (C) 



Fed. No. 0564.88 

 Fed. No. 059.89 



Heegeri series (c) 



heteris rhomboidea tenuis simplex | heteris rhomboidea tenuis simplex 



i 



boi 



98 



1032 



317 



32 



302 



67 



36 

 331 

 102 



13 



78 

 21 



5 



45 

 19 



2 



13 



4 



11 



13 1 



70 



C:c 



1.9.9:1 

 24.2 : ] 

 16.9:1 



Total 

 Expected 



1447 

 1368 



401 : 469 : 112 

 456 : 456 : 152 



69 

 63 



19 

 21 



21 

 21 



21.9: 

 3.0: 



