No. 7. — The Early Embryology of Ciona intestinalis, Flem- 
ming (L)! By W. E. CASTLE. 
CONTENTS. 
PAGE 
I. Introduction . 208 A. Early Stages of Gastru- 
II. Material, Life History 205 lation ^s . 
III. Methods 4 ‘ 213 (a) 112-cell Stago ; 
1. Killing, Preservation 218 (b) Differentiation of 
2. Decortication, Staining, the Principal Or- 
Mounting . 214 gans as seen at 
IV. Maturation and Fertilization P ALT the 112-cell Stage 
Summary on Maturation and a. Topographical . 
Hertilizatlom cic ao a 223 B. Histological 
V. Polarity of the Egg . . . 224 B. Later Stages of Gastru- 
Summary on Polarity of the lation 
Aj da . 220 (a) From 112- cen to 
VI. Cell Lineage of the Embryo . 9926 128-cell Stage 
1. Nomenclature . . . 226 (b) Closure of the Blas- 
2. Cleavage . ‘ 227 topore . 
A. Early Stages of Glony- C. Summary on Gastrula- 
age . . 227 tion 
(a) To 24- cell Stage « 227 4, Formation of the faia ‘ 
(b) Summary on Early Summary on Formation 
Cleavage Stages. 234 of the Larva 
B. Later Stages of Cleav- VII. Discussion of some Theoreti- 
age .. 235 cal Questions . . . 
(a) From 24. cell to 40- A. Origin of the Germ Darin 
cell Stage 235 of Chordates . 
(b) 48-cell Stage . 237 B. The Colom Theory 
(c) 64-cell Stage . 239 C. Ancestry of the Chordates 
(d) 76-cell Stage . 240 | VIII. Conclusions . . 
(e) Summary on Later IX. Table of Cell Lineage . ` 
Cleavage Stages. 242 | Literature Cited 
3. Gastrulation . . . i 248 | Explanation of Plates 
I. INTRODUCTION. 
267 
272 
275 
280 
So long ago as 1866, Kowalevsky wrote, “ Die Entwicklungsgeschichte 
der Ascidien wurde schon vielfach studirt.” 
If this statement was true 
1 Contributions from the Zoölogical Laboratory of the Museum of Comparative 
Zoölogy at Harvard College, under the diréttion of E. L. Mark, No. LII. 
VOL. XXVII. — NO. 7. 
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