ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 491 



Histogenesis of Nerve-fibres.* — W. His has studied this subject 

 on human embryos. In one only, 2 • 15 mm. long, it was found that 

 the nucleated bodies of the cells of the medullary plate were already 

 more crowded towards the central canal, early marking the central 

 position of the ganglion-cells. The cells send out processes, most of 

 which extend radially ; hence the majority of the cells, but not all, 

 are bipolar. Perhaps the irregular outrunners are amoeboid processes. 

 There is at this stage nothing which can properly be called nerve- 

 fibres. In an embryo of 5 mm. in length, the number of cells in the 

 spinal cord is greatly increased. They lie closer together, thickest 

 centrally, and their nuclei, except in the peripheral portion, have for 

 the most part their long axes running radially. Throughout the cord 

 there is a system of radial fibres, many of which may be seen to be 

 prolongations of the cells. The fibres form a more or less well- 

 marked external layer around the cord ; their external ends generally 

 present a trumpet-like enlargement. The roots of the nerves are 

 formed by the outgrowth of these fibres. The motor roots are first 

 developed. They appear as processes of the ventral cells of the 

 cord, penetrate the limiting membranes, and so enter the body-wall. 

 The posterior roots arise later. His believes that the cells which 

 Balfour, Sedgwick, and others have described as forming the beginning 

 of the roots are merely those which grow out to become the ganglion 

 cells distributed in the course of the nerves. 



Olfactory Lobes in Vertebrates and Higher Arthropoda-f — 

 Professor G. Bellonci's results are stated briefly as follows : — The 

 olfactory lobes have the same essential characters in the above two 

 groups of animals. The so-called olfactory glomeruli are character- 

 istic of this region of the brain, and consist chiefly of a close nervous 

 reticulum formed by the olfactory nerve-fibrils and the processes of 

 the olfactory cells. The external relations of the olfactory lobes 

 now discovered include a constant and most important connection 

 with the optic region, as already described by the author in the higher 

 Crustacea and with cerebral regions possessing high psychical 

 functions, as is known to occur in Mammals also. These relations 

 show an essential agreement to exist between the structure of the 

 brain of Vertebrata on the one hand, and Arthropoda on the other ; 

 and this agreement depends on physiological requirements common 

 to the two groups. Professor Bellonci concludes with some theo- 

 retical considerations having reference to the. complete similarity in 

 structure and connections which function is able to produce in the 

 same organs of different types of animals. The animals studied 

 were Squilla, Gryllotalpa, Anguilla, and Bana. 



Colouring Matter of Egg-shells.| — This subject has already been 

 dealt with by Wicke, Sorby, and Liebermann. C. F. W. Krukenberg 



* Arch. f. Anat. u. Physiol., Anat. Abth., 1883, pp. 163-70 (1 pi.)- Cf. Science, 

 (1883) pp. 467-8. 



t Atti E. Accad. Lincei, Trans., vi. (1882) pp. 302-3. 



X Veriiaudl. Phys. Med. Gesell. Wurzburg, xvii. (1882) p. 109. Cf. Natur- 

 forscher, xvi. (1883) pp. 144-5, 



