130 PROF. E. RAY LANKESTER ON [Feb. 5, 



also evidence of their existence in a plaster cast of another 

 specimen which passed through the hands of Messrs. Rowland 

 Ward & Co. 



An examination of the figures given in Plate VI. shows that 

 in all four ossicones (the I'ight and left of two adult male Okapis) 

 the free terminal region is smooth and polished, forming a cap of 

 about half an inch in length, whilst this region is followed by a 

 rougher substance, furrowed on the surface. The polished region 

 projects beyond the skin, the rougher region is clothed by the 

 living integument. In all there are very deep horizontal fissures 

 in the polished material of the " cap." These fissures are some- 

 what irregular in form, and it is impossible without making a 

 section (which I had not permission to do) * through the solid 

 material to ascertain their depth. They are of the same nature as 

 those shown in the text-figure in section (text-figure 49, p. 126). 



I think there can be little doubt that these transverse fissures 

 are caused by the ingrowth of the living tissue after the pro- 

 trusion of the dense polished cap, so as to cut ofi" the protruding- 

 portion and provide for its breaking ofi" — just as an antler is cut 

 off and prepared for disruption in the Oervidfe. A small conical 

 piece is thus thrown ofi" from the end of the horn or ossicusp, and 

 may be regarded as a rudimentary or minute "antler." 



But the process of discarding these minute points or antlers in 

 the Okapi appears to difier from what occurs in the Cervidse, not 

 onlv in the minute size of the discarded segments, but in the fact 

 that the preparation for the breaking ofi' a second (and even a 

 third) segment takes place before the first piece has been got rid 

 of. The living tissue having absorbed the bony matter by a 

 horizontal ingrowth and having created a transvei'se break in the 

 continuity of the osseous substance (see text-figure), recedes for a 

 distance of a sixth of an inch or less, and then again penetrates 

 inwards, forming a new horizon of disruption ; and from the 

 appearance of the specimens figured in Plate VI., especially figs. 4 

 and 5, it seems that this process of the recession of the living- 

 investment of the horn-tip and the subsequent ingrowth of the 

 living tissue, may be again repeated before the most anterior 

 piece is broken off, so that these horizontal fissvires are visible on 

 the surface of the horn-tip, following one another somewhat 

 irregularly. 



* Since reading this paper, I have been kindlj' permitted by the authorities of the 

 Royal Scottish Museum to examine the horns of one of the specimens above refei-red 

 to by making a section of the tip of the horn. The piece cut out has been drawn 

 and then carefully replaced and cemented in position, so that no injury is done to the 

 specimen. The skull lent to me by the Royal Scottish Museum is that of which I had 

 already drawn the horn-tips in figs. 1 to 8, Plate VI., before it had passed from 

 the possession of Messrs. Rowland Ward & Co. The sections drawn on an 

 enlarged scale in text-figs. 52 & 53 explain themselves. It is seen that the grooves 

 or fissures visible on the surface do not extend very deeplj^ but that there is evidence 

 of resorptive activity in the form of certain branching canal-like structures lying 

 deeply within the bony matter, which have probably been excavated by resorptive 

 ingrowths from the soft surface tissues. 



