OOGENESIS AND FERTILISATION. 
Gen. Sub . 19 
Dkiesgit, II. Entwicklungsmechanische Studien. i. Der Werth der 
beiden ersten Furchungszellen in der Echinoderm-Entwicklung. 
Experiraentelle Erzeugung von Theil- nnd Doppelbildungen. II. 
Ueberdie Beziehungen des Lichtes zur ersten Etappe der thierischen 
Formbildung. Z. wiss. Zool. liii, pp. 160-184, 1 pi., 2 figs. 
If one of the two first cells of the segmenting ovum of Echinus micro- 
tuberculalus be isolated, it segments as if it were a half of the intact 
embryo, but eventually forms an entire individual of half the normal 
size. 
Eigenmann, 0. H. On tho precocious segregation of the sex cells in 
Micrometrus aggregates , Gibbons. J. Morph, v, pp. 481-492, 1 pi. 
In the development of the Teleostean Micrometrus aggregates the repro- 
ductive cells are segregated from the surrounding cells about the time the 
blastopore closes. 
Fiedler, K. Entwicklungsmechanische Studien an Echinodermeneiern. 
Sep. Abd. Festschrift IC. W. v. Niigeli und A. v. Kolliker. Zurich : 
1891, pp. 191-196. 
Slight injury to one of the two first cells of the segmented ovum of 
Echinoids sometimes resulted in small but normal embryo ; but in most 
cases not even the blastula stage was reached. 
Fol, II. Contribution a l’etude de la fecondation. O.R. cxii, pp. 877- 
879, 10 figs. 
The sperm-nucleus forms a spermocentre ; the ovarian pronucleus 
forms an ovocentre ; after “solar” and “aureolar” phases, the spermo- 
centre and the ovocentre are divided into halteres. In the next phase the 
spermocentre and the ovocentre are divided, and the halves go through a 
“ marche du quadrille.” Fertilisation consists not only in the addition of 
two demi-centres derived from the parent organisms, but in the union of 
two demi-spermocentres with two demi-ovocentres to form the two first 
astrocentres. 
. Die “ Centrenquadrille,” eine neue Episode aus der Befruchtungs- 
geschichte. Anat. Anz. vi, pp. 266-274, 10 figs. 
. Sulla quadriglia dei centri ; un episodio nuovo della fecondazione. 
Atti [Rend.] Acc. Rom. vii, pp. 431-434, 10 figs. 
*Gastel, L. Contribution il l’etude des follicules de Graaf et des corps 
jaunes. Paris : 8vo, 54 pp., 1 pi. 
Giacomini, E. Ueber die Entwickelung von Seps chalcides. Anat. Anz. 
vi, pp. 548-551. 
^Guignard, L. Sur la nature morphologique du phenomene de la 
fecondation. C.R. Soc. Biol, iii, pp. 467-470. 
IliECKER, Y. Die Richtungskorperbildung bei Cyclops und Gantho- 
camptus. Biol. Centralbl. xi, pp. 668-670. 
