76 
James Small. 
o! a complete chromosome from the nucleus (cp. Gates on Oenothera 
mut .lata and mut. gigas, 18), but the suggestion may be useful. 
The rapidity with which some of the elements break up to 
form the next of the series is analogous to the unstable mutants 
which De Vries suggests may intervene between successive stable 
forms, and which are said to be specially noticeable when mass 
mutation takes place (3). The analogous changes in the plant 
might take place either during nuclear division or in successive gen¬ 
erations ; the former case might well lead to the very marked 
mutations which are supposed by Willis (IV, 93) to occur, since the 
different stages in the disintegration of the parent would not be 
identified with corresponding external stages. 
Polyphyly of genera or even of species, which is becoming 
URANIUM 1 
%ri a 
Uranium Xi 
55 5 DAYS 
UfiAN/UM X* 
/•6'5 Mins. 
Uranium H 
3 « /0 6 /cars 
Ionium 
2 « /0 5 y ms 
Radium 
2440 yfARS 
Emu at ion 
5 55 ms 
Radium f \ 
4 '3 him s 
Radium 6 
38 -5 Mins. 
Radium C 
28-1 Mini. /3 
Raoiuii C' 
/O' 6 StCS 
Radium D 
, %4 yms v 
Radium L 
7-2.0 mys 
(ZADIUrt F 
/9Q o/\yS 
£nD ( ruM - art / 
Fio. 41. Uranium-Actinium Disintegration Series 
Uranium y 
i-2 days 
Uranium Z 
5Tl LL V/iK«OW* 
Actinium 
? 
Radio-Actinium 
281 m w 
Actinium X 
16 A days 
Emanation 
5-6 secs. 
Actinium A 
0- 00 3 secs . 
Actinium fi 
5S.-I mins. 
Actinium C 
31 m«s. 
Em ( Zl0 
