10 PROCEEDINGS OF THE NATIONAL MUSEUM VOL. 97 
colored or may be banded longitudinally in some regular pattern 
giving a bicolor, tricolor, or quadricolor effect, or it may be irregularly 
banded, or simply show a mixture of differently colored hairs; indi- 
vidual hairs of tail may be unicolor or show from two to ten bands 
of color. 
No truly melanistic individuals are included among the squirrels 
described under the subspecies headings. In Sciurus granatensis 
chrysurus of Bogot& a more or less blackish phase appears, with a 
melanistic individual noted. 
MOLT AND SEASONAL CHANGE 
Judged from the appearance of individuals in various stages of molt, 
it appears that the colors and patterns of the new pelage of one season 
are not necessarily faithful reproductions of those of the corresponding 
season of the previous year. It seems that the amount of white or 
red on the ventral surface will vary from season to season in any one 
representative of a group where both red and white undersides occur; 
that the color and pattern of an individual may shift from one of the 
categories listed above to another one if both colors and patterns 
occur in the population; that an individual with a uniformly colored 
tail one season may have a black-tipped or distinctly bicolor one the 
next, provided such variation exists in the group to which it belongs. 
Such changes appear to represent phases of a long and complex cycle 
correlated with the physiological changes attending growth, breeding, 
and senescence, and with the individual or group response to environ- 
mental fluctuations. 
Such morphological changes are known to occur among mammals 
of the temperate zones and have been consistently studied. At 
present the determination of seasonal changes in pelage and color 
pattern in any species of tropical-zone mammal is difficult and in 
most cases practically impossible. Nearly all specimens of tropical 
American mammals in our collections represent small series taken 
within a very short period of time. Where we do find a large series 
taken during a period of time covering two or more calendar seasons, 
we may find also that the locality given on the labels of the specimens 
represents, in reality, an immense area that harbors a number of diverse 
populations. Each of these populations, in turn, may be subjected 
to a different ecological season within the same calendar period. 
Among the squirrels of the present collection under study, only one 
series, that taken from the middle Rio Cesar region, lends itself as 
most nearly suitable for throwing some light upon the question at 
hand. ‘This series of 66 specimens includes 27 from the Rio Guaimaral, 
a channel of the Cesar, and 39 specimens from E] Orinoco, Rio Cesar. 
The names of the localities represent different camps about 5 kilo- 
meters apart in the same general area. The squirrels were taken 
within a radius of 5 kilometers from each camp. 
