146 EINAR LÖNNBERG, MAMMALS COLLECTED BY THE SWEDISH ZOOLOGICAL EXPEDITION ETC. 
out that »the darkening of the centres of the blotches» as well as »their total blacke- 
ning» has been repeatedly observed in the Southern Giraffe. Some races like G. c. 
tippelskirchi of German East Africa, and G. c. wardi of Northern Transvaal remain 
in the stage with star-like spots, and it is of interest to note that such a stage is 
found as well among the Giraffes with a well developed frontal horn (tippelskirchi), 
as among those with the frontal horn rudimentary (G. c. wardi). In a later stage 
of development the blotches become more compact and larger. This is effected by 
deposition of more pigment in the periphery of the spots especially in the interspaces 
between the irregular processes of the star-like blotches. Finally an increase in size 
takes place by the confluence and combination of several adjoining blotches into 
larger dark areas. That these latter really have originated in such a way as descri- 
bed is proved by the fact that remnants of the formerly existing light interspaces 
between the primary constituents often can be seen in the shape of radiating light 
streaks here and there. It is such remnants of former light interspaces between 
primary spots which are described by LYDEKKER' as >»lighter tripartite radiating lines 
in the larger» spots of G. c. rothschildi. Tt is thus not »a tendency to split up into 
stars» as the author quoted says, which makes itself known by these radiating lines, 
but exactly the opposite, a confluence of spots into larger areas. Even in G. c. 
reticulata, which represents the last stage in this series of development of pattern, 
similar light streaks radially cutting into a large dark area may be seen (conf. Pl. 
VIT, fig. 3), although comparatively rarely. A good proof for the confluence of pri- 
mary spots into larger dark areas is given by the fact that very often such areas 
show not one but several such dark centres which are commonly seen in the pri- 
mary spots or blotches. Very good illustrations to this are to be found in LYDEK- 
KBER”S paper in Proc. Zool. Soc. London 1904 Vol. I, for instance PI. XII G. c. roth- 
schildi S, Pl. XV fig. I the neck of G. c. cottoni, and Pl. XVI G. c. capensis g. 
There appears to be no doubt whatever that the development of the pattern of 
the Giraffes has taken place in such a way as I have tried to set forth above. The 
cause of this development is, however, more difficult to indicate. It has already 
been stated that it cannot have been natural selection for protective purposes. 
It is a very common thing among Ruminants that the adult are darker than 
the young, and especially the bulls have a tendency to blacken with age. TItis also 
a fact that some of the most specialised types among the larger ruminants in the 
adult stage of both sexes are quite strongly pigmented. It is thus only in accor- 
dance with a general rule among Ruminants that the adult bull Giraffes are darker 
than the young and immature. It appears also to be in agreement with the condi- 
tions prevailing in other groups that this general darkening which from the begin- 
ning only was found in the old males by and by extends to both sexes. But if the 
starting point is something like a young G. c. tippelskirchi with comparatively pale 
and jagged star-like spots, and an increase in the pigmentation takes place with the 
darkening spreading from the centre of the spots it is quite natural that a pattern 
similar to that of G. c. reticulata will be a final result. 
oe TOO NO: 
