THE ORIGIN AND BEHAVIOR OF THE CENTRO- 
SOMES IN THE ANNELID EGG. 
A. D. MEAD. 
CONTENTS. 
PAGE 
Te GENER AUB occ cec opm accceneces gente sonsecuecnenonnataonecadeenansosavaccknursnatesnnanntnsndpreedscc=nnccasnantieee 181 
(a) Zhe Morphological Relation of the Centrosome to the Other Organs of 
FY CHUL ne oA ere ac cE ce P Ep © eae oe eee ry eee Ape ccE cee rere Eon -> 182 
(b) Zhe Function of the Centrosomes in CHIBI EROTLO TE rere ane ee ene 188 
IJ. DESCRIPTIVE........--- Soe eS cat ee ee reper beet coe crececr ee atsew sec aeceoctee 192 
(a) Collection and Preparation of Material .......--2-..------- SP eee Aen ee 192 
(b) Method of Fixing and Staining ...-ce-cceecorene veces cennnennnen cesennne nae 193 
(c) Origin of the Maturation-Spindle 2-12 21--veeerenenneennnnnnnee nena 193 
(d) Observations upon the Unfertilized Living Eggs... 2 LOT 
(6) Fertilization ..secccccneenenseeeccreennenceeeeeceeecninnniesnecnmncenanane ceennesaeease tease 198 
VG, Spo U Se pe ete ce eee ence eee: rer ere pee eee raaereceeber soceet beer bene beeectcic AO) 
I. GENERAL. 
No protoplasmic structure has been the object of greater 
interest or incited more investigation during the last few years 
than the centrosome. The fact that it remained undiscovered 
until a comparatively recent date, and that, with modern 
technique, it has been found to occur in cells representing 
many different tissues in a variety of animals and plants, 
would alone place the centrosome in a conspicuous position in 
the literature on the cell; but the difficulty and uncertainty 
often attending the demonstration of this structure, its minute- 
ness, the variety of phases under which it manifests itself, the 
diversity and supreme importance of the functions attributed 
to it, either as the bearer of hereditary qualities or as the 
organizer and director of cell-activities, have stimulated re- 
search and discussion to an extraordinary degree. 
The literature on the centrosome has developed two general 
problems toward the solution of which the results of these 
observations are contributed. 
