140 FOOT AND STROBELL. [Vol. II. 



living, e.g., chromo-acetic,^ strong osmic acid, platinum chlo- 

 ride. Fourth, the amount of shrinkage caused by the fixative 

 is dependent upon the stage of development reached by the ^^^, 

 the unfertilized egg being much more sensitive to the fixative. 



The hundreds of eggs that we have measured have served 

 merely to impress us with the fact of the inconstant effect of 

 the fixatives and subsequent technique — this inconstancy 

 speaking for the individuality of each egg. As shrinkage 

 must be an important factor in determining the final distribu- 

 tion of the cytoplasmic elements, we hope to be able to collect 

 enough data on this point to be of service. 



Photomicrography. 



Preface. — In the autumn of 1893 and the winter of 1894, 

 my friend Dr. Charles G. Fuller, of Chicago, successfully pho- 

 tographed a full series of my sections of the egg of Allolo- 

 bophora foetida, illustrating successive steps in the maturation 

 and fertilization of the &gg.'^ 



The work was done with the Zeiss horizontal photomicro- 

 graphic camera, Zeiss microscope with apochromatic condenser, 

 Zeiss projection oculars 2 and 4, and Zeiss apochromatic lenses 

 16-2 mm. immer., 140 aperture. Artificial light was used. I 

 am glad of this opportunity to express my indebtedness to 

 Dr. Fuller. The good quality of his work will speak for itself 

 when the photographs are published. 



These photographsf were shown at Woods Holl in the sum- 

 mer and early autumn of 1894, and, as far as I am aware, they 

 were the first photomicrographs of sections showing the proc- 

 esses of maturation and fertilization of the egg. — Katharine 

 Foot. 



Our work has been done with a Bausch and Lomb verti- 

 cal photomicrographic camera, Zeiss microscope, apochromatic 



1 In 1896 (5) I regarded chromo-acetic as the most reliable fixative, giving as 

 one reason for this, that eggs measured before killing, and after mounting, gave 

 almost the same diameter. At that time I had not measured the eggs at each step 

 in the technique, and the measurements were not extended to sections. — K. Foot. 



- As these photographs have no especial bearing on the details discussed in this 

 preliminary, I shall reserve their publication for a future paper. 



