EARLY DEVELOPMENT OF JULUS TERRESTRIS. 45] 
Borax carmine stained well in the earlier stages, while the ovum 
was still in the ovary, and also in later stages, when the embryo 
was far advanced in development; but in the intermediate stages, 
between about the tenth day and hatching, was wholly useless ; 
staining the yolk-spherules equally with the nuclei. Hema- 
toxylin was better, staining the nuclei deeply; but it also 
stained the smaller yolk-spherules so as to make it a difficult 
matter in some cases to distinguish between them and the 
nucleoli. The best fluid was alum-carmine prepared after 
Grenacher’s method. This fluid has the advantage of staining 
the nuclei and nucleoli with a different tinge to that of the 
yolk-spherules, and the result was most satisfactory. The diffi- 
culties in the way of observing the course of development were 
many and were only overcome by cutting a great number of 
sections, only about one series in twenty being perfectly satis- 
factory. 
The warmth of the weather had a great influence on the rate 
of development; one clump of eggs, for instance, was hatched 
on the twelfth day after being laid, while another was not 
hatched till the twenty-fifth. As the shorter period seemed to 
be the most usual, I worked out a clump of eggs which hatched 
on the twelfth day, and preserved a number each day, using 
the results as a standard by which to estimate the progress of 
development in other ova. 
I propose in the present paper to begin with the ovum in 
the ovary after it has attained a fair size and to trace its deve- 
lopment up to the time of hatching, leaving for a future paper 
its further development to the adult animal. 
The Ovarian Ovum. 
The ovum within the ovary is surrounded with a follicular 
envelope derived from the cells of the ovary. It has a large 
nucleus and a single large nucleolus, within which it is usually 
possible to make out two or three vesicular spaces. The body 
of the ovum stains slightly. The nucleus is large and distinct, 
stains slightly, and when viewed under a high power (;'; oil 
