ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
189 
Histogenesis of Nerve-cells and Neuroglia.* * * § — Signor G. Valenti, 
in studying the development of the nervous system in Elasmobranch 
fishes ( Mustelus , Torpedo, &c.), finds that the epithelial cells of the 
medullary canal give origin by indirect division to the embryonic 
neuroglia • that from the cells of the embryonic neuroglia there arise 
by various and gradual transformations the nerve-cells and neuroglia- 
cells of the adult ; and that from the mesoblastic connective tissue around 
the canal some elements enter the outer layers of the cord and become 
neuroglia-cells. 
0. Histolog-y. 
Terminology of Cell-division.f — Prof. W. Flemming regards “ the 
formation of scientific terms as a necessary evil,” but in this paper he 
adds to the list. This is done in order to secure clearness in the future, 
and with special reference to Fol’s objection that the term “ aster ” has 
been used by Flemming in a sense different from that for which he 
(Fol) originally used it. So Flemming will henceforth substitute for 
“ Aster ” and “ Dyaster ” the terms “ Astroid ” and “ Dyastroid.” 
Nucleus and Cell-substance during Mitosis.f — Dr. H. F. Muller 
finds, from observations on the elements of the blood in the spleen of 
Triton, that after the disappearance of the nuclear membrane in mitosis 
the cell-substance mingles with the nucleus. He believes that this 
intermingling is of importance in the physiology of indirect division. 
The Intermediate Body in Cell-division.§ — Dr. A. Geberg describes 
in the dividing cells of the cornea of Triton a minute intermediate body, 
like Flemming’s Zwisclienlcorperehcn. The nuclei of the two daughter- 
cells were in the dyaster stage ; the slight residual part between the 
two cells contained a minute corpuscle from which radiating threads 
appeared to rise. 
Amitotic Division in the Spermatogonia of Salamandra.|| — Herr 
F. Meves finds that amitotic division often occurs, especially in March 
and in September and October, while mitotic division also occurs, rarely 
in spring, more frequently in autumn, and predominantly from May 
till August. This periodicity suggests that the amitotic division is not 
necessary to the normal regeneration of the testes. The behaviour of 
the annular attractive sphere during the fragmentation of the spermato- 
gonium-nucleus suggests that it exerts a mechanical influence in the 
division. 
Indirect Division.! — Prof. J. Frenzel describes in the mid-gut gland 
of Carcinus msenas and some other Crustaceans, a process of cell-division 
which is amitotic, but associated with a halving of the nucleolar sub- 
stance. It is a “ nucleolar nucleus-halving.” 
He notes that the epithelial cells of the mid-gut usually divide 
without mitosis, and that while half of the mother-cell is discharged, 
* Atti Soc. Tosc. Sci. Nat., vii. (1891) pp. 385-0. 
t Anat. Anzeig., vii. (1892) pp. 26-32. 
X S.B. K. Akad. Wiss; Wien, c. (1891) pp. 179-88 (1 pi.). 
§ Anat. Anzeig., vi. (1891) pp. 623-5 (1 fig.) 
|| Tom. cit., pp. 620-39 (11 figs.). 
Archiv f. Mikr. Anat., xxxix. (1892) pp. 1-32 (1 pi.) 
1892. 
r 
