-Q- 



I wish to express here my gratitude to my friend 

 Dr. Ross G, Harrison for placing at my disposal the material 

 from which the younger stages of development were made out : 

 to Prof i^ ^§imon iH, Gage for the really considerable amount of 

 trouble he took in aiding one who was, at the time, wholly un- 

 knov/n to him, to obtain the older stages for this work: and to 

 Prof ^ Frooks for much valuable aid and many suggestions during 

 the progress of the work. 

 y •£: rinunc; I obtained the best results by killing in 



Corrosive Acetic (95o.c. saturated solution of HgCl and 5c. c* 



2 

 glacial acetic acid) , hardening in the usual alcohols and stain- 

 ing, in toto, with Borax Carmine and, on the slide, with Lyons 

 Blue. The greatest technical difficulty experienced was in ob- 

 taining good preparations of the long, gland cells. Embryos 

 were fixed in a number of ways, but in no single case was a good 

 preparation of the gland cells obtained. Maceration was tried 

 also, but with no success. Gome difficulty was experienced also 

 in sectioning the earlier stages, on account of the mass of yolk, 

 but with later stages there was no trouble of this kind. 



All the sections were drawn with a camera, though in 

 most cases the details had to be filled in from a series of sec- 

 tions. 



