calary and may serve to illustrate a possible mechanism 
by which some of the knobs which were once terminal 
became subterminal. 
Abnormal chromosome 10 differs from normal chromo- 
some 10 inthe greater length of its long arm and in the 
greater proportion of heteropycnotic chromatin in its dis- 
tal segment. Longley (17) reported this type of chromo- 
some in corn and Chapingo teosinte and gave two possi- 
bilities as to its origin: 
The origin of the much-knobbed, longer types of chromosome X might 
be the result of the addition of a fragment marked by both a terminal 
and an internal knob, or the picture might be reversed by considering 
that the normal short types have resulted from the loss of a terminal 
portion of the long arm of the long types. 
There can be no doubt as to the meaning Longley in- 
tended to convey —that one of the two possibilities was 
the simple addition of a fragment. Longley (18) contin- 
ued to refer to this type in corn as having ‘‘an additional 
piece on the end of the long arm,’” without revising his 
original explanation. It may be noted that Longley’s 
interpretation of the origin of this chromosome was given 
in 1937, five years after Burnham’s (7) discovery that a 
certain translocation previously reported as simple was 
in reality reciprocal, and three years after Sharp (44) had 
stated that Burnham’s discovery ‘‘naturally raises a ques- 
tion regarding other supposed simple translocations. ’’ In 
other words, Longley’s suggestion that abnormal chro- 
mosome 10 might be the result of the simple addition of 
a fragment naturally leads to the inference that he was 
aware of the widespread belief that broken ends are incap- 
able of attaching themselves to natural ends, but that he 
regarded this case as an exception to the rule. Randolph 
himself recently (81, 32) contributed what might be re- 
garded as two different views on the question. In the first 
paper cited, he states that normal ends ‘‘ordinarily”’’ do 
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