212 DR. H. GADOW ON THE EVOLUTION [Mar. 18, 



and composition with the pedicle and antler of the Cervince. 

 The homologue of the antler has, since Sandifort, been called the 

 OS cormc, and it forms by far the greater mass of the whole bony 

 cone. It has ah-eady been stated that it is continuous with the 

 pedicle, so much so that in many species of Oavicornia, especially 

 of Oxen, the sinuses of the diploe extend far into the cone, in old 

 animals far towards the apex. Occasionally the os cornu ossifies 

 from a special centre, separate from the frontal bone. It is, 

 however, short-lived as a separate entity. A. Brandt found it in 

 lambs as a small bony nodule, which could be lifted out of a corre- 

 sponding cup-shaped depression of the frontal bone in very young 

 animals. It fuses with the rest when the lamb's horns are perhaps 

 3 cm. long. Nitsche found it in the kid of a Chamois whose 

 horn- sheath was only 2 cm. long, and he adds that it is already 

 firmly fused with the frontal bone in the first autumn. I myself 

 have several times come across specimens of ewe- skulls which had 

 been bleaching for a long time on the Welsh hills, and in which 

 the upper lamina of the frontal bone had fallen ofi" at the precise 

 spot which normally carries the horns. There is no pedicle in 

 these specimens, but this absence is due to the feebly developed 

 state of the horns of these ewes, which as a rule do not carry such 

 organs. In calves, even the youngest, a separate os cornu is 

 unknown, but they occur sometimes, pathologically, in polled or 

 hornless cattle as ever-growing bone loosely attached to the head 

 by the suiTounding skin. It is a great mistake to imagine that 

 the occasional separate ossification of the os cornu is a primitive 

 feature. 



The normal development of the calf's head-gear is as follows : — 

 Slight elevation of the frontal bone into a comparatively broad- 

 based but low pedicle. This is surmounted by a shallow cone 

 composed of fibrous connective-tissue and cartilage. The cartilage 

 has its growing -point near the apex. The perisclerium is con- 

 tinuous with the periost of the pedicle portion. Ossification 

 proceeds from the pedicle upwards, transforming the soft growth 

 into a bony cone, the cartilage being gradually restricted to the 

 apex. The last traces of cartilage vanish when the horns are 

 between one and two inches in length, and the os cornu then 

 continues to grow by the ordinary subperiosteal mode, young con- 

 nective-tissue continuing to proliferate especially at the apex. 

 Blood-vessels enter from the pedicle and from the periosteum. 

 The periosteum passes imperceptibly into the I'est of the cutis. 

 Vertical sections of a young " horn " half an inch in length 

 show all the minutest features in diagrammatic clearness. The 

 specimens were decalcified in picric and nitric acid, then cut and 

 stained with the triple stain of Erlich-Biondi, with hsematoxylin 

 and picric acid, or with thyanine. 



Outside is the dense mantle of horn passing towards the 

 Malpighian layer into the chai'acteristic comb- shaped jagged 

 processes in the act of transformation into horn, each of the 

 processes resting upon a finger-shaped extension of a cutis- papiUa.. 



