ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1 5 1 



and the connection between them is of a primary nature. The Btapes 

 cannot be homologous with any structure found in the lower Vertebrata, 

 for it is derived from the first arch, whilst the amphibian and reptilian 

 stapes is either derived from the auditory capsule or from the second 

 arch, like the hyomandibular of fishes. The malleus and incus are 

 homologous with the articulare (in part) and the quadrate of the lower 

 groups. 



Development of Red Blood Cells in Chick.* — C. Price-Jones finds 

 that the nucleated red cells of the fowl's blood originate in the embryo 

 from primitive mesoblast cells, and develop by successive stages of 

 " primitive erythroblasts," " metrocytes," and " daughter-cells," that 

 result from repeated cell-generations. In each generation a large pro- 

 portion of the cells have insufficient vitality to attain maturity, and in 

 consequence suffer degeneration ; the proportion is greater among the 

 more primitive cells. The author suggests the possibility that the pro- 

 ducts of each successive series of degeneration may constitute the 

 stimulus for the development of less primitive forms into the next 

 higher condition of cell, or may be the origin of anti-bodies to the 

 primitive forms, constituting an immunity to these forms and inhibiting 

 their further production. 



Development of Subdivisions of Pleuroperitoneal Cavity in Birds.t 

 Margaret Poole has re-investigated this subject, and confirms the results 

 of Bertelli and of G. W. Butler. She also compares the subdivisions of 

 the coelom in reptiles and birds, noting, for instance, that on the whole 

 the condition in the Orocodilia seems to approach most nearly to that in 

 birds, yet the manner of the exclusion of the lungs from the peritoneal 

 cavity in the latter is far more like what occurs in Testudo, and probably 

 also in the Varanidas. 



Development of Vertebral Column in Grass Snake.J — Erna 

 Briinauer finds that in Tropidonotus natrix the first primordium of the 

 axial skeleton appears in the form of band-like thickenings, the hints of 

 the bases of the arches, the transverse processes, and ribs. The vertebras 

 arise from the perichordal sheath and are at first distinguishable from the 

 bases of the arches, with which they subsequently fuse. The chondrifica- 

 tion proceeds from three groups, one in the centrum, the others in the 

 dorsal part of the neural arch. Ossification is prefaced by the degenera- 

 tion of the cartilage in the centre of the centrum. The deposition of 

 bony lamella? proceeds from the ventral and dorsal aspects of the 

 centrum, and from four spots on the neural arches. The inter-vertebral 

 ring appears in early stages as a boundary line in the sclerotome. It 

 consists of fibrous connective tissue and becomes implicated in the 

 articulation. The notochord shows inter-vertebral constrictions ; in the 

 course of development it is almost completely constricted, first within the 

 joint and then in the vertebral region as well. In the trunk region 

 there are unpaired intercentra ; in the tail they form paired inferior 

 arches, pushed cranium-wards on the centra. 



* Journ. Pathol. Bacteriol., xiv. (1909) pp. 218-23 (1 pi.). 



t Proc. Zool. Soc. London, 1909, pp. 210-35 (14 figs.). 



\ Arb. Zool. Inst. Univ. Wien,xviii. (1910) pp. 133-56(2 pis. and 2 figs.). 



