Royal Microscopical Society. 9 



granules soon become osteoblasts in the basi-facial and basi-cranial 

 regions of the bird, and the " parasphenoid " (j>a. s.) and " basi- 

 temporals" (b. t.) are the result of this histological change. 



Jn the Lizard, which is extremely unlike the Bird in many 

 respects, there is a rudimentary azygous " parasphenoid," but in 

 place of the " basi-temporals " we have a delicate ectosteal lamina of 

 bone immediately investing that part of the " basilar plate " from 

 which the notochord has retired. The space between these two 

 true " basi-sphenoids " in the Lizard is the " posterior basi-cranial 

 fontanelle." 



In the less magnified figure of the Tit's face (Fig. 7) below 

 and behind the end of the gelatinous layer (g. I.) the " para- 

 sphenoid " (pa. s.) is spreading, bifurcating, and grafting itself upon 

 the basi-sphenoidal cartilage (b. s.). This extraneous bone under- 

 takes the bone-leavening process for the anterior part of the " basi- 

 sphenoid," and then runs outwards and backwards from the apices 

 of the " trabeculae," and grows into large temporal wings that wall- 

 in each trumpet-shaped " anterior tympanic recess." The " basi- 

 temporals " (Fig. 2, b. t.) undergird the skull where its floor is 

 open — the " posterior fontanelle," and send their beautiful diploe- 

 fibres round the internal carotid arteries and the tongue-shaped 

 rudiment of the " cochlea." They thus form a lower floor beneath 

 the true " occipito-sphenoidal synchondrosis." 



It may be a very simple matter to take an adult bird's skull and 

 with a fine saw cut it into sections that shall resemble ordinary ver- 

 tebra?, but such easy parlour-work throws no light upon all that 

 series of changes which laborious morphological work reveals. Some 

 happily-constituted minds, anatomical lotos eaters, enjoy a soft and 

 soothing sense of things in this delicious way. Hawng mentioned 

 other vertebrate types, Fishes, Keptiles, Mammals, &c, and their 

 likeness and unhkeness to the Bird in the modes of their develop- 

 ment, I may remark that a sense of the real Unity of the whole sub- 

 kingdom grows upon me. It makes me giddy to look farther down, 

 and I turn my " deficient sight," for rest, to the exquisite fitness in 

 the results of all those darkly-wise processes, all which " are placed 

 in number, weight, and measure," and which, working together to 

 one common end, in the upshot, produce the most charming of all 

 living creatures. 



Another addition to the first prae-oral arch is the vomer 

 (Fig. 4, v.) ; this is composed of two delicate bony styles, formed 

 by ossification of a small cartilaginous nucleus on each side, and 

 afterwards grafted upon the vestibular part of the nasal sac ; the 

 two ossicles have already united at the mid-line in front. But the 

 main secondary element of the first arch is the " prae-maxilla " — 

 longest of the bird's facial bones ; here, in the Tit's (Fig. 4, px.), 

 it is less than in any other bird, with the exception of the Swift 



