FEBRUARY 22 1901.] 
A Study of the Phenomena of Cleavage in Ether- 
wed Eggs : EK. B. WILson. 
The Influence of the Germ Cells upon the Som- 
atic Cells: G. W. FIEp. 
Two Improved Forms of Automatic Microtomes : 
C.S. Minor. 
A Study of the Phenomena involved inthe Chem- 
ical Production of Parthenogenesis in Sea Ur- 
chins: HK. B. Wi1son. 
Centrosomes and Spheres in the Maturation, Fer- 
tilization and Cleavage of Crepidula: EK. G. 
ConKLIN. 
Independence of the Germ Nuclei in Cleavage. 
A New Method of Preservation of Fragile Speci- 
mens: A.D. Mrap. 
Larval Stages and Metamorphosis of the Hermit 
Crab: M.T. THompson. 
Regeneration in Planaria maculata : 
BARDEEN. 
Cc. W. 
Histogenesis of the Peripheral Nervous System 
R. G. Harrison. 
in Salmo salar : 
SCIENCE. 
297 
Asexual Reproduction of Planaria maculata 
W. C. Curtis. 
Variation in Hydromeduse: C. W. Harerrr. 
The relative Proportion of the Sexes in Poultry: 
G. W. FIEp. 
Notes on Variation in the Shells of Purpura 
capillus: R. P. Bigetow and H. S§. 
Conant. 
Variation and Elimination in Philosamia 
cynthia: H. HK. CRAMPTON. 
The Tentacles of Gonionemus: H. F. PERKINS. 
Tos. H. MonrcomeEry, JR., 
Secretary. 
THE PROJECTION OF RIPPLES BY A GRATING. 
AFTER obtaining the condition under 
which one grating is projected by another, 
it seemed not unlikely that the method 
might be used for projection of ripples. If 
the latter are obtained in a trough of rect- 
angular outline, the light reflected from 
them breaks up into two series of equi- 
The Mesentric and Spermatie Arteries of Didel- 
phys Virginiana: C. F. W. McCroure. 
Observations upon the Regeneration of Renilla : 
H. B. Torrey. 
Certain Points in the Structure of the Lower 
Vertebrate Brain: J.B. JoHNSON. 
distant bright lines intersecting each other 
orthogonally. Hence the first grating * 
may be dispensed with, being replaced by 
*See preceding article, SCIENCE, XII., pp. 617- 
627, October 26th, 1900. The bars of the grating G 
must be parallel to the projection of ripples at S, both 
being vertical lines like the axis of G. 
