398 D. J. SCOURFTELD ON MENDELISM AND MICROSCOPY. 



ing the other he called the " dominant " character. In the list 

 given above.it is the first-named of each pair which lis* the dominant 

 character — thus, round are dominant over wrinkled peas, yellow 

 over green, and so on. To the characters which failed to appear 

 in the hybrids, Mendel applied the term " recessive," because he 

 wished to suggest that, as he clearly showed to be the case, the 

 characters thus described (or rather, the factors in the germ-cells 

 representing them) were not actually annihilated, or even altered, 

 but that they simply failed to manifest themselves in the presence 

 of the dominant characters. 



Mendel next planted the seeds from the first crosses and allowed 

 the plants so raised to be self-fertilised. He then found that the 

 recessive characters reappeared without any alteration, and in a 

 proportion very closely approximating to one-fourth of the whole. 

 Thus, out of every four plants belonging to the second generation, 

 three on the average exhibited the dominant character and one 

 the recessive character of the particular pair united in the 

 original cross from which they were descended. As examples of 

 the actual numbers obtained, the following will suffice : 5,474 

 round and 1,850 wrinkled seeds; 6,022 with yellow, and 2,001 

 with green cotyledons; 882 inflated and 299 constricted pods. 

 The net result of all seven pairs of characters gave a proportion 

 of 2-98 to 1. 



Proceeding in accordance with his proposed plan of work, 

 Mendel again planted his new crop of peas, and, after the self- 

 fertilisation of the plants, obtained a third generation,* which 

 showed that the dominant forms of the previous generation, 

 although apparently all alike, had really been of two types. One 

 of these, comprising on the average one-third of the total 

 dominants, proved to consist of pure dominants — i.e. no recessives 

 were produced ; the other type, comprising the remaining two- 

 thirds, consisted of hybrids producing progeny in the proportion 

 of three dominants to one recessive in the same way as the 

 original hybrids. The recessives of the second generation proved 

 to be pure, for they produced no dominants in the third genera- 

 tion. This kind of work was carried on for as many as six 



For the sake of brevity, the different generations are now usually 

 referred to as F„ F.„ F 3 , and so on, meaning the first, second, third, etc., 

 filial generation from the parental generation which is indicated 03- the 

 letter P. 



