146 EINAR LONNBEEG, 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 0. c. 

 tippelskirchi of German East Africa, and 0. 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 Lydekkeb^ as »lighter tripartite radiating lines 

 in the larger* spots of G. c. roihschildi. It 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. PI. 

 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- 

 ker's paper in Proc. Zool. Soc. London 1904 Vol.1, for instance PI. XII G. c. roih- 

 schildi cT, PI. XV fig. 1 the neck of G. c. cottoni, and PI. XVI G. c. capensis c?. 



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. It is 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 prevaiHng 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 spreadi^g 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. 



1 L. c. 1904, p. 210. 



