J. W. Jenkinson 
207 
were examined by means of sections. Further, according to him, the Plane of 
Symmetry always includes the "penetration" path, and always becomes the Sagittal 
Plane (here I cannot help thinking he goes too far). The relation between the 
Planes was further investigated by puncturing the egg in the two-celled stage. 
When the First Furrow coincided with the Plane of Symmetry the result was 
a hemiembryo lateralis, when at 90° to the Symmetry Plane a hemiembryo anterior 
(the blastomere not containing the grey crescent having been iujured) and when 
oblique an embryo with one posterior side wanting. 
In a second communication {Arch. Ent. Mech. xxii. 1906) the effect is described 
of removing part of the vegetative hemisphere by puncture. When this operation 
is performed prior to the formation of the grey crescent subsequent development is 
normal. Up to this time therefore the egg is isotropic about its axis. When the 
grey crescent has appeared, however, the loss of this substance may entail abnorn)ality 
or death. 
LITERATURE. 
(1) Agassiz, a. Embi-yology of the Cteiiophorae. Mem. Amer. Acad. Arts and Sciences, N.S., 
X. 1873. 
(2) Born, G. Ueber den Einfluss der Schwere auf das Froschei. Arch. mikr. Anat. xxiv. 
1895. 
(3) BovERi, T. Die Entwickelung vou A scar is megalocephala mit besonderer Riicksicht auf 
die Kernverhaltnisse. Festschr. Kuppfcr. Jena, 1899. 
(4) . Die Polaritait von Ovocyte, Ei und Larve des Strongylocentrotus Hindus. Zool. 
Jahrh. {Anat.), xiv. 1901. 
(5) . Ueber die Polaritat des Seeigeleies. Verh. d. phi/s.-med. Ges. zu Wiirzburg, xxxiv. 
1902, 
(6) . Ueber die Abhangigkeit der Kerngrosse und Zellenzahl der Seeigel-larven von der 
Chromosomenzahl der Ausgangszellen. Jena, 1905. 
(7) CoNKLiN, E. G. The organization and coil-lineage of the Ascidian egg. Journ. Ac. Nat. 
Sci. Philadelphia, xiii. 1905. 
(8) . Mosaic development in Ascidian eggs. Journ. Exp. Zool. ii. 1905. 
(9) Crampton, H. E. Experimental studies on Gasteropod development. Arch. Ent. Mech. 
III. 1896. 
(10) Driesch, H. Entwicklungsmechani.sche Studien. i, ii, Zeitschr. wiss. Zool. liii. 1892. 
in— VI, Ibid. LV. 1893. vii— x. Mitt. Zool. Stat. Neapel, xi. 1895. 
(11) . Die isolirten Blastomeren des Echinidenkeimes. Arch. Ent. Mech. y.. 1900. 
(12) Driesch, H. and Morgan, T. H. Zur Analysis der ersten Entwicklungsstadien des 
Ctenophoreneies. xirch. Ent. Mech. ii. 1896. 
(13) FiscHEL, H. Experimentelle Untersuchungen am Ctenophorenei. i. Arch. Ent. Mech. vi. 
1898. II— IV, Rid. vii. 1898. 
(14) Foot, K. Preliminary note on the maturation and fertilization of tlie egg of Alloloho- 
phora fortida. Journ. Morph. iX. 1894. 
(15) Garbowski, M. T. Ueber die Polaritat des Seeigeleies. Bull. Internat. dc I'Acad. des 
Sci. de Cracovie. 1905. 
