158 
function which persist through one or more generations after the cause of 
the alteration has ceased to operate.” 
Since the variations herein reported occur in structures purely vege- 
tative and result from no intervening sexual act, they are in kind compar- 
able with vegetative variation known elsewhere—bud variation, etc.— 
with the exception that since the mycelium, consisting of a single row of 
cells, is the seat or origin of the variations the case is morphologically 
simpler than where tissues are involved, as in bud variation. De Vries 
(122) classes bud variations in general with mutations in that they appear 
as clear-cut discontinuous variations. Many examples of vegetative 
variation have been studied extensively and reported upon under the 
terms mutation, saltation, sporting, etc. Cramer (37) gives a very com- 
plete summary of the known cases in 1907. East (46), Stout (120), Ghys 
(61) and Shamel, Scott, and Pomeroy (102, 103) give reports, with ex- 
tended bibliographies, concerning bud variation in the potato, Coleus, 
chrysanthemum, and lemon among the phanerogams. The transmission 
of such variations in the potato has been carefully studied by East (47, 
48, 49) with the general conclusion that these asexually appearing varia- 
tions concern characters that Mendelize in sexual reproduction. In the 
Pteridophytes, Benedict (16) reports saltation in the Boston fern. Dobell 
(43) summarizes the evidence from some twenty-eight papers concern- 
ing variability among the bacteria, discussing them in two categories: (1) 
physiological mutations, that is, changes in power to produce ferments 
or pigments; and (2) morphological mutations. He closes the first part 
of his discussion as follows: “It seems legitimate to conclude from the 
foregoing facts that some races of bacteria are able permanently to acquire 
new characters under certain conditions.”” He considers only two cases 
of morphological mutation, citing the work of Barber (7), who produced 
a race of long bacteria by single-cell selection, and of Revis (94), who 
claims to have produced a new race of Bacillus coli by the use of malachite 
green. Both Laurent (76) and Le Poutre (77) conclude that by passage 
a harmless bacterial species may acquire real virulence. An extensive 
résumé of the question of mutation in the bacteria is also given by Baerth- 
lein (5). Numerous variations of yeasts, both morphological and phys- 
iological, are reported by Guilliermond. (62). 
The validity of the conclusion maintaining that there is mutation 
among the bacteria and yeasts has been attacked by Brierley (28) on the 
ground that the changes reported as mutations are merely due to segre- 
gation of organisms of aberrant type from an originally mixed popula- 
