JOURNAL 
OF THE 
ROYAL MICROSCOPICAL SOCIETY. 
DECEMBER 1895. 
SUMMARY OF CURRENT RESEARCHES 
Relating to Zoology and Botany (principally Invertebrata and Crypto- 
gamia ), Microscopy, &c., including Original Communications from 
Fellows and Others .* * * § 
ZOOLOGY. 
VERTEEEATA : — Embryology, Histology, and General. 
a. Embryology.! 
Placenta Circumvallata.t — Dr. O. von Herff finds that the circum- 
vallate and marginate placenta is due in part to a primarily too shallow 
imbedding of the ovum, and in part to inflammatory degenerative pro- 
cesses in the decidua, &c. Both factors usually occur together. 
Evolution of Vertebral Column.§ — Dr. H. Gadow has published an 
abstract of his conclusions on this subject. He points out that the key 
to the solution of the composition of the vertebral column is given by 
the metameric repetition of four pairs of symmetrically arranged carti- 
laginous elements. In the earliest primitive condition four pairs of 
arcualia are present, either as separate pieces, or the basidorsalia and 
basiventralia fuse. In the next stage the interventraliar pieces are 
reduced, and the other three pairs either remain separate or co-ossify. 
Reductions may occur further in the interventralia, basiventralia, or 
interdorsalia. Dr. Gadow believes that the ribs are homologous struc- 
tures throughout the Vertebrata. They are lateral distal outgrowths 
of the original basiventralia, with which they later on form joints ; they 
ossify independently. 
Development of Hypochorda and Pancreas in Frog.|| — Dr. Ph. Stohr 
finds that in Rana temporaria the hypochorda arises as a median thicken- 
ing of the dorsal wall of the gut, being constricted off from in front 
* 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. 
f This section includes not only papers relating to Embryology properly so called, 
but also those dealing with Evolution, Development and Reproduction, and allied 
subjects. t Abh. Nat. Ges. Halle, xx. (1894) pp. 231-56 (1 ph). 
§ Proc. Roy. Soc., lviii. (1895) pp. 257-9. 
II Verh. Anat. Ges. IX. Vers., x. (1895) pp. 176-80. 
1895 2 s 
