44 Inheritance and Evolution in Orthoptera II 



there is no possibility of proving the matter, unless a form without it, 

 or only heterozygous for it, should be discovered. 



There are two classes of characters, the one such SiS A, B, C, D, etc., 

 in Paratettix, pea and single in combs of fowls, and round and wrinkled 

 in peas, and the other class such as B in Paratettix, <J> in combs of fowls 

 and A in colour of the albumen in peas. In the first class two factors 

 for any one suffice to make the whole character, and two for different 

 ones produce a hybrid, intermediate in fact, though the one may be 

 more apparent (epistatic) and the other less apparent (hypostatic). 

 Two factors for either A, B, C, or either of the others in that series, 

 suffice for a complete pattern ; one factor for one and another factor for 

 another make a hybrid. Two factors for pea make a complete pea 

 comb ; two factors for single produce a complete single comb ; while 

 one factor for pea and one factor for single produce the hybrid comb 

 (with pea epistatic, though this hybrid is said to appear somewhat 

 intermediate). Two factors for roundness produce the character of 

 roundness, two factors for wrinkledness produce a wrinkled pea; one 

 factor for wrinkledness and another for roundness produce an inter- 

 mediate in fact (with the round epistatic, though this hybrid is said to 

 be somewhat intermediate). In the other class (@, <1> and A) no one 

 can exist except in connection with, and in addition to, characters of 

 the first class. As already stated these factoids are allelomorphic to their 

 absences, never to any other character. For instance, in Pat^atettix, 

 when BB contains a 'single dose of @ (heterozygous for it), in the 

 gametogenesis, every other gamete receives a dose of @, half the gametes 

 formed carrying it and half without it. In neither case does the @ factor 

 affect the normal behaviour of the B gamete. The same conditions 

 prevail for hybrids, such as BG ; if @ be present in the single dose, only 

 every other gamete receives it, if @ be present in double dose, no gamete 

 is formed without it. In either case the gametogenesis in BG proceeds 

 as though @ were not present. (In the use of the word " dose " or 

 " fector " there is no intention at this time of attempting to convey any 

 conception of the condition or situation in the germ cells of the factor 0.) 

 It requires two gametes of any one multiple allelomorph to make a 

 homozygote for that form, or a gamete of one and a gamete of another 

 multiple allelomorph to make a hybrid or heterozygote. The situation 

 is entirely different with regard to such characters as ©, in Paratettix, 

 fp in combs of fowls and A in colour of peas; these are mere appur- 

 tenances of the gametes of the multiple allelomorphs. 



This conception, if acceptable, has wide application. Besides applying 



