CELL DIVISIONS, DURATION OF INTERKINETIC
STATES
AND DIFFERENTIATION
IN EARLY STAGES OF
EMBRYONIC
DEVELOPMENT
T. A. DETTLAFF
A. N. Severtsov Institute of Animal Morphology, Academy of Sciences of
the U.S.S.R., Moscow
Introduction
323
I. Cleavage Divisions. Periods of Synchronous and Asynchronous Division
325
II. Interaction between the Nucleus and the Cytoplasm during the Period of
Cleavage
326
III. Morphogenetic Action of Nuclei during the Period of Asynchronous Cleavage
Division
328
A. Development of Cell Competence and Inducing Capacities
328
B. Onset of Gastrulation
329
C. Morphogenetic Activity of Nuclei and the Number of Cell Divisions
330
IV. The Ratio of the Duration of Different Developmental Periods
331
A. Duration of Cleavage
331
B. Relationship of Cleavage Processes and Gastrulation in Haploid and
Polyploid Embryos
333
C. Relative Duration of the Periods of Gastrulation and Neurulation
336
D. Deviations from Typical Ratios of the Durations of Various Developmental Periods
337
E. Ratio of the Durations of Cell Division, Gastrulation and Neurulation in
Various Representatives of Amphibians and Sturgeon Fishes
340
V. Morphogenetic Role of the Differences in the Ratio between the Durations of
Cleavage, Gastrulation and Neurulation
345
A. Latent Differentiation in the Embryos of one Species developing at
Different Temperatures
346
B. Effect of Li Ions
348
C. Effect of Temporary Isolation of the Embryonic Material in Physiological Solution
349
D. Importance of the Duration of the Interkinetic State and Number of
Cell Divisions for the Process of Latent Differentiation of the Entoderm
350
E. Latent Differentiation of Rudiments in Embryos of Different Systematic
Groups
351
VI. The Ratio of the Rate of Processes of Latent Differentiation in the Derivatives
of Different Germ Layers in Amphibian Embryos
355
VII. Summary
358
References
360
The problem of the relationships between cleavage and differentiation
in the embryonic development of animals arose at the very source of
Introduction
323