MEMBRANE AND CARTILAGE BONES 165 



morphological significance of the distinction between 

 membrane and cartilage bones, and in IS5O 1 he defended 

 his views against the criticisms of Reichert 2 in a further 

 note entitled Die Theorie des Primordialschadels festgeJialten. 

 It is convenient to consider these papers together. Kolliker 

 held that there was (i) a histological and (2] a morphological 

 difference between the two categories of bones. The histo- 

 logical development of the two kinds was different, but this 

 difference was not sufficient to establish a morphological 

 distinction between them, a distinction in their anatomical 

 Bedeutung. The true morphological distinction between 

 them was their development in different skeleton- forming 

 layers. Membrane bones were developed in fibrous tissue 

 lying between the skin and the deep layer which formed 

 the primordial cranium, and it was this formation in a 

 separate layer that gave them a different morphological 

 significance from the bones formed directly in the deep 

 layer. Kolliker's distinction, therefore, was between the 

 bones formed in the primordial cartilaginous cranium on 

 the one hand, and the superficial ossifications in fibrous 

 tissue on the other hand. The cartilaginous cranium in 

 Kolliker's opinion was formed upon the vertebral type, and 

 the membrane bones were accessory. This, at least, was 

 his opinion in 1849. In 1850, after Stannius had shown 

 that membrane bones occurred as integral parts of the 

 vertebrae in certain fish, he modified his view of the mem- 

 brane bones, and admitted them, at least in some cases, as 

 constituents of the cranial vertebrae. 



On this morphological distinction of membrane and 

 cartilage bones future comparative osteology was to be 

 based : 



" My sole aim is to state again the principle upon which 

 comparative osteology is to be based and extended, and this 

 is that first place should be assigned to anatomical considera- 

 tions, and among these to the manner of origin of the whole 

 bone in relation to the skeleton-forming layers" (1850, p. 

 290). 



The homologies established by this new principle might 



1 Zeits.f. iviss. Zool., ii., pp. 281-91. 

 - Muller's Archiv for 1849, PP- 443-5 I 5- 



