802 THE AMERICAN NATURALIST. [Vor. XXXV. 
discrete lines of development, the two former starting from con- 
ditions of plesiobiosis, the latter from the widespread instincts 
of ants to prey on the offspring of other Formicide. Other 
cases which obviously resemble true dulosis may have arisen 
from xenobiosis. This appears to be true of cases like Zepto- 
thorax emersoni and possibly also of the species of Strongy- 
lognathus and Tomognathus. On the other hand, the cases of 
colacobiosis may be conceived to have originated either from 
xenobiotic conditions like that of Z. emersoni or from dulotic 
conditions like that of Strongylognathus testaceus. I cannot 
believe that Forel or Lubbock really intended their sequence 
as anything more than a rather general attempt in concrete 
language to account for the phylogenetic derivation of the 
remarkable cases of social parasitism (Anergates) from the 
simpler forms of mixed nests. It is therefore superfluous to 
waste many words for the sake of showing that the ants of the 
Forel-Lubbock series are not phylogenetically related. It is 
not only easier to sketch the phylogeny of the compound and 
mixed nests in bold outlines than to fill in the details, as Was- 
mann somewhat reproachfully suggests, but this is the only 
available method of procedure at the present time. Still even 
the attempt at detailed speculation in this direction scarcely 
merits our disapproval as it does Wasmann's, for free and 
open speculation is necessary to the advancement of a scien- 
tific subject, if only as furnishing the necessary incentives 
and guides to the attainment of profounder insight. Mere 
fact-culling is not and never can be science. 
Another argument on which Wasmann lays some stress is 
drawn from the supposed immutability of instinct! The 
instincts of F. sanguinea and Polyergus are regarded as iden- 
tical both in Europe and America, and these instincts must 
therefore have remained unchanged for a very long period of 
time (9L p. 249). “Huber’s amazons of 1804 fought and 
! [t is unnecessary in this place to deal with the doctrine of the immutability 
of instinct so brilliantly advocated by Fabre ('79—00). That it is quite unten- 
able has been demonstrated by Dr. and Mrs. Peckham ('98), Whitman (99), an 
others. It could, in fact, be demonstrated to be false from Fabre's own mag 
nificent observations. The genus Leptothorax, considered below, furnishes addi- 
tional evidence, if this were needed. 
