ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 395 



Peculiar Hair Structures.* — K. Toldt, jun., describes the peculiar 

 epidermic covering on the tiat grooved bristle-spines in Platacanihomys 

 lasiurus, an arboreal Myoxid from Malabar and Cochiu-China. In the 

 shallovr broad groove there are scale-like cells, differing greatly in their 

 strength, form, and disposition. The author also discusses longitudi- 

 nally grooved hairs. Sometimes the grooving is restricted to the cortical 

 area ; sometimes there are ridge-like projections of the cortex into the 

 medulla, while typically the outer surface remains ungrooved. 



Structure of Hypophysis. f — L. Edinger finds in man that all the 

 cells of the hypophysis are surrounded by lacunae, which unite between 

 cells and adjacent blood-vessels to form long secretory tubules. These 

 tubules open into the perivascular lymph-spaces of the infundibular 

 vessels, and thence extend into the mass of the brain. 



Comparative Study of Thymus. | — J. Salkind has studied the 

 minute structure of the thymus in mammal, bird, reptile, amphibian, 

 and fish. It is a complex organ, retaining an embryonic character in 

 part, and consisting of an endodermic syncytium with digestive pro- 

 perties, and of a mesodermic reticulate tissue with a leucopoietic role. 



Structure of Bird's Lung.§— A. Juillet gives a detailed account of 

 the structure, disposition, and development of the bronchi in the lung 

 of the l)ird, and gives some histological description as well. The bronchi 

 in l)irds never end in culs-de-sac ; they are all in inter-communication, 

 forming circuits which can be traversed by pure air, from one end or 

 the other, according as the air comes from air-sacs or from trachea. The 

 pulmonary parenchyma does not form complicated culs-de-sac, with walls 

 covered with alveoli, l)ut a system of delicate bays traversed by blood- 

 capillaries and enveloped by endothehum. Each blood-capillary is sur- 

 rounded on all sides 1)y air. There is a veritaljle vascular labyrinth 

 developed in the three directions of space and penetrated by air on all 

 sides. 



Histogenesis of Egg-tooth. || — B. Rosenstadt finds that the pri- 

 modium of the so-called egg-tooth is an area of the rete malpighii, 

 in which the whole cytoplasm of the cells is changed into horny fi])res. 

 They run longitudinally, transversely, and periDendicularly (from the 

 stratum cylindricum towards the stratum corneum). Even the nucleus 

 is included in tlie cornification. In the formation of the horny covering 

 of the beak, as is usual, it is only the mantle of the cell that is changed 

 into horny fibres, and more or less thin plates result. There never is 

 cornification without the horn-fibre stage being passed through. The egg- 

 tooth and the corresponding rudiment on the mandible appear earlier 

 than the horny bill, and, as has been noticed, their mode of cornification 

 is different. It may be that there are vestiges of a phylogenetically older 

 armature of the jaws. 



* Verb. Zool. Bot. Ges. Wien, Ixii. (1912) pp. 29-32. 



t Verb. Anat. Ges., 1911. Anat. Anzeig., xxxviii. Enganzungsheft, p. 89. 



X Anat. Anzeig., xli. (1912) pp. 145-55 (7 figs.). 



§ Arch. Zool. Exper., xlix. (1912) pp. 207-371 (6 pis.). 



II Arch. Mikr. Anat., Ixxix. (1912) Heft i, Abt. i., pp. 612-36 (1 pi.). 



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