DE, E. EAT LANKESTEE ON OKAPIA, 295 



and a more minute histological study of the cellular origin of the tissues involved, 

 would probably give a decisive result in regard to this question. We have to note 

 that in the case of these cranial bony outgrowths we are dealing with tissues of very 

 special activity and variability. The annual detachment and breaking away of what is 

 admittedly a true outgrowth of the frontal bone in the Cervidge and its regrowth, the 

 suppression of Pecorine horns altogether in races and individuals, as well as their 

 duplication, indicate that these bony growths cannot be in any case regarded as mere 

 processes of the bone of which they form part in the adult. That such was their 

 ancestral origin seems most probable ; but quasi-independence and peculiar nutritional 

 relations have been subsequently acquired by them. 



The theory that the Giraffine and Bovine horn-cores — as distinct from the Cervine 

 antler — have originated ancestrally from independent dermal bones, distinct from the 

 cranial roofing-bones, involves one of two suppositions, viz., either that the dermal 



characteristic histological structure, and is referable to the same class of bony growths as those produced 

 pathologicall}- in cases of rheumatic arthritis. This secondary element of the bony core of the Pecorine 

 horn is seen in a comparatively unmodified condition as the hollow cone-like caps or epipliyses of the horn- 

 cores of Giraffa. I suggest as probable that the caducous portion of the Cervine antler is genetically 

 identical with this epiphysial cap, whilst the base or "Rosenstock" of the Cervine antler is identical with the 

 more or less protuberant boss or tumescence which is a direct outgrowth of the outer tabula of a cranial 

 bone in Giraffidse. In vertical sections now before me of the bony horns of full-grown Giraffes, it is evident 

 that this basal (and more primitive) element of the ossicusp is of considerable volume, and actually rises 

 up some four or five inches, so as 1o form the base and axis of the parietal horns, the epiphysial cap 

 having the form of a holloiv cone which rests on and is fused with this deeper cone-like upgrowth. I find 

 myself in agreement with Dr. Diirst, who recognizes the existence of this truly frontal upgrowth in 

 Cavicornia as " Hornstiel," and identifies it " in gewisser Hinsicht " with the " Eosenstock " of Cervidse. 



The " Hornstiel," or horn-pedicle, or horn-boss, though small, is present in varying degree, according to 

 Dr. Diirst, in all Cavicornia. On the other hand, the " Hornzapf," or horn-cone, of the Cavicornia (as 

 distinguished from the horn-boss) originates as a mass of osteogenetio tissue, separate from that which forms 

 the frontal bone : it constitutes by far the greater bulk of the bony structure of the horn. It seems to me 

 probable that the Cavicorn's bony horn-cone is identical with the hollow conical bony epiphysis or cap of the 

 Giraffe's horn, and, consequently, with the deciduous element of the Cervine antler. In Cavicornia the 

 primitive bony element of the horn, viz. the horn-boss, or Hornstiel, has been further reduced than it is in 

 the Giraffe, and its place is actually taken by the secondary accessory structure — the horn-cone or epiphysial 

 cap. A secondary growth, originally developed as an accessory to a primitive organ, has here (as happens in other 

 instances) acquired overwhelming vigour, and been substituted for the primitive organ, which consequently 

 dwindles and nearly disappears. The Giraffes, with their well-developed cranial horn-bosses and relatively 

 small epiphysial horn-caps (Hornzapffen) are intermediate between the Cavicorns and a primitive group 

 which had no epiphysial horn-caps, but only horn-bosses (Hornstiele). Our immature Okapia is actually 

 in the latter condition, and it seems (so far as adult specimens can allow one to judge) that the horn-cores 

 of the long-extinct Dinocerata also were true horn-bosses of the cranial bones and not epiphj'sial — that is 

 to say, not " Hornzapffen," or horn-caps. — E. E. L., April 30th, 1902. The actual mode of growth of the 

 frontal " ossicusps" three inches in length, revealed in the adult Okapi recently received in Brussels, has yet 

 to be ascertained.— May 23rd, 1902. 



VOL. ivi. — PART VI. No. 3. — August, 1902. 2 u 



