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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. Embryolog-y.f 
Developmental Mechanics.t — Dr. Hs. Driescli describes, under 
the title of “ developmental-mechanical studies” — a phrase by no means 
above criticism — some experiments on the segmentation of the ova of 
Echinus and on the influence of light on the segmenting ova of Echinus, 
Planorbis and Bana. If one of the two first cells of the segmenting 
ovum of Echinus microtuberculatus be isolated, it segments as if it were a 
half of the intact embryo, but eventually forms an entire individual half 
the normal size. “ Thus the principle of organ-forming germ-areas 
is contradicted, and the possibility of artificially producing twins is 
proved.” In regard to the second set of experiments, it seems that light 
has no perceptible effect on the processes of segmentation or formation 
of organs. 
Dr. K. Fiedler § describes some experiments on “ developmental 
mechanics,” in which the segmented ova of Echinoids were punctured or 
shaken so as to isolate some of the cells. Slight injury to one of the 
two first cells of the segmented ovum sometimes resulted in small but 
normal embryos. But in most cases the result was that not even the 
blastula was reached. In three cases when one of the first two cells 
was destroyed, the remaining cell attained to a semi-blastula stage, and 
in two cases to what might be a semi-gastrula. 
* 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 Zeitschr. f. Wiss. Zool., liii. (1891) pp. 160-84 (1 pi.). 
§ Sep. Abd. Festschrift zur Feier des fiinfzigjahrigen Doctor- Jubilaums der 
Herren Prof. Dr. K. W. v. Nageli und Prof. Dr. A. v. Kolliker, Zurich, 1891, 
pp 191-6. 
