[Annals N. Y. Acad. Sci., Vol. XIV, No. 3, pp. 165-246, Oct. 31, 1903.] 



THE EARLY EMBRYOLOGY OF THALASSEMA 

 MELLITA (CONN).^ 



John Cutler Torrey. 



Contents. p^^^e. 



Introduction 166 



I. Cell Lineage TO Gastrulation 169 



1 . To 64 cells 170 



2. Further Divisions of the Quartets 179 



a First Quartet 179 



<^ Second " 181 



c Third " 183 



d Fourth and Fifth Quartets 184 



3. Special Considerations 185 



a Prototroch 185 



b Variations in Cleavage 1 90 



c Equal and Unequal Cleavage 192 



II. Gastrulation to Trochophore 195 



1 . Gastrulation 195 



2. Closure of the Blastopore 195 



3. History of the Dorsal Gap in the Prototroch and of the Shifting of Em- 



bryonic Areas 199 



4. Formation of Enteron 204 



5. " of Oesophagus 207 



6. Differentiations of the Ectoderm 209 



HI. Fully Developed Trochophore 211 



a Ectoderm 211 



b Ciliation 212 



c Alimentary Tract 213 



d Mesoblast 213 



e Excretory Cells 216 



/ Habits 216 



IV. The Mesoblast 218 



1 . Ccelomesoblast 218 



2 . Ec tomesobl ast 223 



V. Rudimentary Cells 231 



1 Submitted in partial fulfilment of the requirements for the Degree of Doctor 

 of Philosophy, in the faculty of Pure Science, Columbia University. 



165 



