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Heredity and Environment 



FIG. 50 a. SYN APSIS (CONJUGATION) OF CHROMOSOMES in the grasshopper 

 Phrynotettix. A. At the left, Telophase of Spermatogonium showing 

 chromosomes in nucleus, among them X and a pair B. At the right, are 12 

 pairs of B chromosomes in synapsis, each pair from a different animal, 

 and one member of each pair from the father, the other from the mother. 

 Homologous chromomeres (granules I, 2, 3, 4, 5) are shown in each 

 chromosome. B similar stages in chromosome pair A. Some of the 

 chromosomes in the middle show a "secondary" longitudinal split and a 

 "crossing over" (?) of the halves. C. Tetrads (conjugated chromosomes) 

 of pair B formed by shortening and thickening of the chromosome pairs 

 and by the appearance of the "secondary" split. (After Wenrich.) 



ing digits of the left hand, and the conjugation of homologous 

 chromosomes may be compared to the placing together of the 

 two hands* so that homologous digits come together. 



In some instances it can be proved that one member of each 

 conjugating pair of chromosomes comes from one parent and the 

 other from the other parent, and it is probable that this is always 



