80 
R. Ruggles Gates. 
disjunction of that pair in meiosis, i.e., AB $ + ABB<? , or (2) that 
an AAB egg (i.e., having 8 chromosomes) is fertilised by a BB sperm 
BB 
resulting from a segregation in meiosis in lamarckiana or (3) 
nn 
ABB 
that the segregation in the megaspore AAABB is —— , the ABB 
A A 
megaspore surviving and being fertilized by a sperm AB, i.e., the 
normal type, to give an AABBB individual. 
While it is thus possible for a new extra chromosome to arise 
in the offspring of lata or lata x lamarckiana, yet the chances are 
considerably greater that the same one will remain the extra one. 
The probability of such forms as exilis and exundans depending on 
the same extra chromosome as lata, depends on their frequency in 
the offspring of lata, which is at present unknown. 
Returning now to the lata- like forms, de Vries (1909) described 
a form which he called semilata, and this arose three times 
independently from lata. One of them when selfed gave 358 
offspring, of which 3 were nanella, 4 lata, and the remainder semilata. 
There is some reason 1 for believing that this form may perhaps 
have had 16 chromosomes. On the other hand, the writer 
described what afterwards proved to be a different form 2 under 
the name semilata. This stands midway between lata and 
lamarckiana, has 15 chromosomes and is only known to arise from 
lata x lamarckiana. When selfed this semilata gives semilata 
(15 chromosomes), lata (15 chromosomes) and lamarckiana (14 
chromosomes). 8 The relation between these two 15-chromosome 
types is therefore a close one, and the differences between them 
can hardly be due to the presence of a different extra chromosome. 
It is conceivable, for example, that semilata might arise from a lata 
egg having 7 chromosomes + a lamarckiana male cell with 8, 
derived through a fresh irregular division. But this explanation 
would appear to apply better to other 15-chromosome mutants. 
Semilata appears rather like a somewhat modified lata, and the 
fact that, as shown elsewhere 3 it exhibits a series of stages running 
on the one hand towards lamarckiana and on the other towards lata, 
supports this view. We may therefore suppose it originates from 
an 8-egg -f a 7-sperm. 
Another important fact in this connection is that (E. scintillans, 
another mutant from Lamarckiana, in now known (Hance 1918) to 
1 See Gates, 1915a, p. iii, footnote. 
2 l.c., p. 112. 
3 Gates and Thomas, 1914, p. 532. 
