CONTINUITY OF THE RACE 



609 



extra chromosome ( n plus 1 ) while another 

 will be short one (n minus 1). II fertiliza- 

 tion occurs with normal gametes, one off- 

 spring will possess an extra chromosome 

 in each cell while another will be short 

 one. The latter probably will not develop 

 whereas the former may show variations in 

 the resulting trait because the genes are 

 doubled. There have been many cases of 

 heteroploidy, as this condition is called. 



This phenomenon of extra chromosomes 

 includes the addition of complete sets, so 

 that gametes possess a diploid instead of 

 the usual haploid number, and in some 

 cases ( particularly in plants where the phe- 

 nomenon is better known) even 3, 4, and 

 5 extra sets. Organisms possessing more 

 than the diploid number are called poly- 

 ploids. They are usually larger and more 

 vigorous than the usual diploid, hence 

 polyploids have found a definite market in 

 the plant world. Polyploid flowers are much 

 larger and more beautiful than the normal 

 ones. Leaves of polyploid tobacco plants 

 are much larger. Efforts to induce poly- 

 ploidy artificially have been successful. The 

 drugs colchicine or camphor prevent di- 

 vision of the cells but do not interfere 

 with the dividing of chromosomes; hence, 

 the gametes possess the diploid number of 

 chromosomes instead of the normal haploid 

 number. Upon fertilization, the resulting 

 offspring then have a double set of chromo- 

 somes, that is, they are tetraploid. Triploids 

 will result from the union of a diploid 

 gamete with a haploid gamete. Experi- 

 mental breeding of these various polyploids 

 has resulted in the introduction of new 

 strains of plants that have proven very 

 valuable in increasing our food output. 

 Very little is known about the occurrence 

 of polyploidy in animals. Evidence is ac- 

 cumulating that it occurs in at least one 

 protozoan, namely, paramecium. 



HEREDITY AND ENVIRONMENT 



The age-old question of which is more 



important, heredity or environment, stimu- 

 lates the most passionate arguments among 

 people in various walks of life, from educa- 

 tor to the man on the street. The problem 

 has recently become so important a politi- 

 cal issue in Russia that it threatens the pro- 

 fessional life of geneticists living behind the 

 iron curtain. What are the best unbiased 

 answers to the questions rising from such 

 discussions that have come to light so far? 



One should first be concerned with the 

 problem of what is really inherited. Is a 

 child unmusical because his parents have 

 no musical skills or is he unintelligent be- 

 cause his parents possess a low order of 

 intelligence? Is a starved child short and 

 underdeveloped because his parents are 

 likewise starved and poorly developed? A 

 careful examination of some data should 

 give us an inkling of the answer to these 

 questions. A child placed in an environment 

 in which every opportunity is afforded him 

 to study music as well as other cultural 

 subjects may show unusual artistic talents 

 and intellectual achievement even though 

 he might not appear to have inherited 

 such ability. Likewise, well-fed chfldren of 

 starved, stunted parents often exceed them 

 in height and physical vigor by a consider- 

 able margin, as has been demonstrated so 

 many times when children of immigrants 

 are larger and more robust than their par- 

 ents, who matured on inadequate diets. In 

 these instances was it the environment or 

 was it heredity that played the more im- 

 portant part? 



It is clear that the children inherited a 

 set of genes which provided the capac- 

 ity to reach these goals. The environment 

 was merely the factor which determined 

 whether or not the genes would be given 

 a full opportunity to express diemselves. 

 Without the substantial set of genes in the 

 first place, no amount of encouragement 

 from a satisfactory environment would 

 have brought them to heights beyond the 

 basic design established by the genes. Of 

 course, the desired goal in any society is 



