Nachdrtick verboten. 



lieber setzungsrecht vorbehalten. 



Developmental History of Primary Segments of the 

 Vertebrate HeadO- 



By 

 Charles Hill. 



With plates 28 — 30 and 4 figures in tetxt. 



Table of Contents. 



I. Introductory. 



1. Review of Literature. 



a) The Mesomeres of the Cephalic Region. 



b) Segments of the Encephalon. 



2. Manipulation of Material. 



a) Living Embryos. 



b) Dissected Specimens. 



c) Sections. 

 IL Descriptive. 



A. Encephalic Segments of Teleosts. 



a) Neural Segments of Salmo observed in Living and Dissected 

 Embryos. 



b) Neural Segments of Salmo observed in Divided Embryos. 



B. Encephalic Segments of the Chick. 



a) Embryos with open Neural Grooves, 1 — 6 Somites, Ages 

 21—25 hours. 



b) Embryos with 6 — 7 Somites, Ages 25 — 26 hours. 



c) Embryos with 7 — 20 Somites, Ages 27 — 40 hours. 



d) Embryos 40 — 100 hours old. 



C. Study of Sections. Chick and Trout, 

 a) Segmental Criteria. 



a) Histology. 



c) Nerve Relation. 



1) Contribution from the Zoological Laboratory of Northwestern 

 University under the direction of Wm. A. Locy. 



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