( 585 ) 
SUMMARY 
OF CURRENT RESEARCHES RELATING TO 
ZOOLOGY AND BOTANY 
(principally Invertebrata and Cryptogamia ), 
MICROSCOPY, &c., 
INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS* * * § 
ZOOLOGY. 
A. VERTEBRATA: — Embryology, Histology, and General. 
a. Embryology. f 
Primitive Segmentation of Vertebrate Brain.J— Mr. B. H. Waters 
comes to the conclusion that the forebrain of Vertebrates is composed of 
at least two well-marked neuromeres. The first nerve arises in the 
same manner as the other cranial nerves, and indicates so far its 
segmental character. From the second neuromere there spring the 
optic diverticula in a manner entirely comparable to the other cranial 
nerves ; this seems to show that, though highly specialized in existing 
Vertebrates, the optic nerve is homologous with the other segmental 
nerves. The midbrain also consists of two neuromeres, from which the 
third and fourth nerves appear to take origin. The hindbrain consists 
of six neuromeres. 
It seems reasonably certain that the central nervous system of the 
primitive Vertebrate consisted of a series of symmetrical segments, all 
of which were intersomitic ; the neuromeres of the head gave origin to 
their respective nerves precisely as did those of the cord to the spinal 
nerves. The striking fact of Vertebrate embryology — the rapid in- 
crease of the anterior brain, and its great differentiation — seems to 
account for the relatively greater size of the fore- and midbrain seg- 
ments, and for their early degeneration ; those, on the other hand, of 
the hindbrain, which remains more primitive in character, persist. 
“ Urmund ” and Spina bifida.§ — Prof. 0. Hertwig publishes under 
this title a study in comparative morphology and teratology based on 
* The Society are not intended to be denoted by the editorial “ we,” and they do 
not hold themselves responsible for the views of the authors of the papers noted, 
nor for any claim to novelty or otherwise made by them. The object of this part of 
the Journal is to present a summary of the papers as actually published, and to 
describe and illustrate Instruments, Apparatus, &c., which are either new or have 
not been previously described in this country. 
t This section includes not only papers relating to Embryology properly so called, 
but also those dealing with Evolution, Development, and Reproduction, and allied' 
subjects. J Quart. Journ. Micr. Sci., xxxiii. (1892) pp. 457-75 (1 pi.). 
§ Arch. f. Mikr. Anat., xxxix. (1892) pp. 353-503 (5 pis.). 
