AUTHOR’S AB3TRACT OF TH13 PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, OCTOBER 13 
Reprinted from Journal of Morphology 
Vol. 33, No. 1, December, 1919 
CHROMOSOME NUMBER AND PAIRS IN THE 
SOMATIC MITOSES OF AMBYSTOMA 1 
TIGRINUM 
CHARLES L. PARMENTER 
Zoological Laboratory , University of Pennsylvania 
THIRTY-SEVEN FIGURES (NINE PLATES) 
CONTENTS 
Introduction. 169 
Technique. 171 
Observations. 176 
A. The number of chromosomes. 176 
a. Method of determining the number. 177 
1. Procedure. 177 
2. Clearness and classification of the complexes. 178 
b. Possible variation in number in uncounted complexes. 181 
c. Abnormal complexes_\.;. 182 
B. Somatic chromosome pairs. 184 
а. Introductory statement. 184 
б. Mensuration. 185 
1. Types of cells. 186 
2. Method. 186 
3. Sources of error. 186 
c. Results of measurements. 191 
1. Criteria for determining pairs. 191 
2. Evidence for the existence of pairs. 194 
3. Summary. 199 
Discussion. 200 
A. Introductory statement. 200 
B. Constancy of chromosome number. 200 
C. Variations in other Urodeles. 206 
D. Variations in other forms. 206 
E. Fragmentation. 207 
F. Existence of pairs. 208 
a. Pairs in the germ cells. 208 
b. Pairs in the somatic cells. 210 
1. Meves’ measurements. 211 
2. Della Valle’s measurements. 215 
3. Results in Ambystoma tigrinum. 216 
c. Constant relative size relations. 220 
d. Summary of measurements. 220 
Summary of conclusions. 221 
1 Also known as Amblystoma. 
169 
