. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. DEVELOPEMENT OF REPTILIA. 639 losa,' with the omphalo-mesenteric vessels ; b is part of the allantois with tlie aUantoic or ' umbilical' vessels, i. The outline of the cara- pace is just marked on the back of the embryo, and the proportion of the vertebral column not so moditied appears to be greater, as is its resemblance to the type-form of Reptile, than in the adult. The condition of the carapace and the outward form of a P'resh- Water Tortoise {Emys) is shown in figure 451. The amnios, a, is turned back to show the p
. On the anatomy of vertebrates. Vertebrates; Anatomy, Comparative; 1866. DEVELOPEMENT OF REPTILIA. 639 losa,' with the omphalo-mesenteric vessels ; b is part of the allantois with tlie aUantoic or ' umbilical' vessels, i. The outline of the cara- pace is just marked on the back of the embryo, and the proportion of the vertebral column not so moditied appears to be greater, as is its resemblance to the type-form of Reptile, than in the adult. The condition of the carapace and the outward form of a P'resh- Water Tortoise {Emys) is shown in figure 451. The amnios, a, is turned back to show the posi- tion of the limbs and head in '*â ''' the egg : b is the part of the allantois ; c the remnant of the yolk. The central opening of the plastron, which is perma- nent in the marine Ohelonia, is seen at this period in all the order, but is quickly filled up in the land and fresh-water species. The chief speciality in the developement of the scaled Eeptiles, compared with each other, relates to that of the carapace and plastron of the Chelonia : and this has been explained at pp. 557-9, and illustrated in figs. 369-72. When the Turtle is hatched, the bones of the head show different degrees of ossification. The premaxillary and preman- dibular are most advanced for the purposes of feeding; the maxil- lary, the back part of the mandible, the prefronto-nasal, frontal, and parietal come next in hardness. The superoccijoital shows an outer layer of bone, the rest being gristle; the basioccipital and basisphenoid begin to be ossified from the centre ; the alisphenoids and exoccipitals are still cartilaginous. The limbs begin to show the digital divisions soon after the carapace is outlined, and the cartilages of the metacarpals and metatarsals are first discernible; the phalanges are composed of compacted polygonal cells at near the term of incubation, which then become ' cartilage cells,' widely divided by blastema. The lone bones of the limbs show a thin outer crust of bone inc
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Keywords: ., bookauthorowenrichard18041892, bookcentury1800, bookdecade1860
