Early Development of the Chinook Salmon 



Matthew C. Riddle, 

 Puget Sound Marine Station, Friday Harbor, Washington. 



CONTENTS 



Introduction and materials ^19 



Description of sperm and egg 3^0 



Segmentation ^^ ^ 



Formation of blastoderm and periblast 323 



From gastrula to embryo 324 



Hatching and fry 325 



Bibliography 3~6 



INTRODUCTION AND MATERIALS 



Scientific investigations upon the Pacific salmon as far as papers pub- 

 lished on the subject would indicate, have been concerned with the nat- 

 ural history and behavior of the salmon and with the growth, development 

 and care of the young fish. Most of the papers dealing with the question 

 of teleost development are concerned with the embryology of pelagic eggs. 

 Henneguy (22) and Klein (28) have investigated the embryology of the 

 trout, Hertwig (21), Ryder (42) and Sumner (44) used Salmonoids as 

 material for embryological study. So far as the writer is aware no work 

 has been done upon the early development of the salmon of the Genus 

 Oncorynchus of which the Chinook salmon (0. tschamytscha) is a species. 

 For this reason this work was undertaken.* The observations recorded are 

 mainly concerned with the external features of development. 



*This work was carried out at the suggestion and under tlie direction of 

 Dr Harrv Beal Torrev of Reed College, to whom acknowledgments are due. 

 The eggs" were obtained thru the kindness of Master Fish Warden R. E. Clanton 

 of the Oregon State Game and Fish Commission, and Mr. LeRoy Ledgerwood, 

 Superintendent of the Oregon State Hatchery of Bonneville. 



The eggs were fixed in Bouins killing agent and preserved in 857'' 

 alcohol. Thus preserved, the yolk coagulated into a hyaline mass. Ben- 

 da's iron haematoxylin was used in staining sections, and eosin and orange 

 G were employed as counter stains. Satisfactory sections were obtained by 

 this procedure. Whole eggs stained with Delafield's acid haematoxylin and 

 mounted in balsam made good preparations. Owing to the large size of 

 the egg, only the cap of the yolk upon which the disk or embryo rests was 

 used in preparing slides. 



(319) 



