The Development of the Heart in Shad. 221 



All the methods of fixation in common use for teleosts were tried. 

 That of Sumner (saturated corrosive sublimate containing 10 per 

 cent glacial acetic; followed by 10 per cent, formalin; see Sumner, 

 '00) proved the most satisfactory and was generally employed; 

 all the figures were drawn from material fixed in this way except 

 Fig. 8 (H. Virchow's method) and Figs. 10 and 11 (Pereny's 

 fluid). ^« 



The embryos were cut into serial paraffine sections ranging from 

 5 to 10 microns in thickness. Sections of the earlier stages were 

 stained with iron hrcmatoxylin, later stages were usually stained 

 in toto with alcoholic carmine. 



Eleven wax-plate reconstructions^^ were made, two hundred times 

 larger than the originals after fixation (correction having been made 

 for shrinkage in paraffine). In making the figures the reconstruc- 

 tions were photographed (natural size) and the outlines of the photo- 

 graph traced. In finishing the drawings the irregularities due to 

 the plates were omitted. All figures, representing reconstructions, 

 have been reduced one-half in reproduction. 



Below follows a list of the figures with data for identification 

 of their sources. (The numbers are from the catalogue of The 

 Wistar Institute of Anatomy) : 



Fig. 1. — Reconstruction 14504, from series 14275, sections 87 to 134. 



Fig. 2. — Outline from embryo afterwards cut into series 14275. 



Fig. 3.— From series 1455G ; 3A section 91, 3B 120, 30 132, 3E 142, 3F 152, 

 3G 181. 



Fig. 4. — Reconstruction 14534, from series 14533, sections 45 to 87; 4A sec- 

 tion 53, 4B 57, 40 02, 4E 71. 



Fig. 5. — Reconstruction 14535, from series 14524, sections 91 to 151 ; 5B 

 section 104, 50 111, 5D 114, 5G 148. 



Fig. G. Reconstruction 14530, from series 14520, sections 03 to 110 ; OB sec- 

 tion 70, GO 79, OD 82, GF 92. 



Fig. 7. — Reconstruction 14.537, from series 14.532, sections 08 to 113; 7B 

 section 82, 70 80, 7D 89, 7G 113. 



"Pereny's fluid, in wliicli, unfortunately, all my material about the time of 

 beginning heart-beat has been fixed, gives fair general results, but is 

 extremely unfavorable for cytological study. 



"Shown at the Chicago meeting of the Association of American Anatomists, 

 Christmas, 1907. 



