SKELETON OF BIMANA. 585 



the superoccipital, and a thicker process behind which becomes the 

 basis of the mastoid. All the above cartilaginous parts are more 

 or less continuous or confluent, and when separate from the un- 

 chondrified extensions of the brain-capsule have been, illogically, 

 termed ' primordial cranium ' (Primordialschadel). But the actual 

 embryonal or primordial skull is originally wholly membranous, 

 and at the stage above described includes parts unchondrified, as 

 well as those showing the intermediate histological conversion into 

 cartilage. The bones, ossification of which begins in membrane, 

 are the basioccipital, vomer, upper half of superoccipital, parietals, 

 frontals, nasals, lacrymals, malars, squamosals, palatines, ptery- 

 goids. A pair of cartilaginous buds from the prefrontals form the 

 piers of the yet unclosed anterior haemal, or ' maxillary,' arch. A 

 pair of cylindrical cartilages, called ' Meckel's,' are developed in 

 the blastemal basis of the tympano-mandibular arch. The body 

 and the stylo-hyal parts of the cornua of the hyoid are gristly 

 before they ossify : much of the cerato-hyal parts of this thin haemal 

 arch retain their primitive fibrous condition. The capsule of the 

 essential parts of the organ of vision is in the same ^ sclerous ' pre- 

 dicament in Man and Mammals : that of the organ of hearing 

 becomes cartilaginous before it ossifies : the perfection of this 

 organ in the well-brained Mammals calls for accessory parts, which 

 show their true nature by their rapid groAvth.^ The true com- 

 prehension of the developemental phenomena of the Human and 

 Mammalian skull is afforded by that of its vertebral archetype : 

 the artificial nature of the classification of the ossified parts into 

 ' primordial skull-bones ' and ^ lid-bones ' (' Deckknochen ') is 

 hereby plainly manifested : it is akin to that which divides them 

 into 'eight bones of the cranium' and ' fourteen bones of the face.' 

 The first seven segments of the trunk consist each of ' centrum,' 

 ' neurapophyses,' fig. 403, n, and ' pleurapophyses,' pi, the ultimate 

 confluence of which forms the bone called ' cervical vertebra : ' 

 the centrum of the first of these coalesces with that of the second, 

 and forms the ' odontoid process :' its place in the ' atlas ' is taken 

 by a ' hypaphophysis.' The pleurapophyses of the seventh cer- 

 vical are occasionally elongated as 'ribs,' fig. 185, A, h. In the 

 seven segments which svicceed the cervicals, the pleurapophyses, 

 pi, are elongated, and retain their freedom ; and after the first they 

 are shifted to the interspace between their own centrum and the 



* The precocious developement of the ear-organ and its complex appendages in 

 Mammals sorely perplex the devotees of developemental phenomena: the superadded 

 bones of the ear-drum, growing straightway to full size, and appropriating much 

 of the blastema of the pleurapophysial or tympanic part of the haemal arch, have 

 been veritable ' will-o'-thc-wisps ' to hunters of homologies on embryological ground. 



