522 
J. S. KINGSLEY. 
caught in copulating, utterly refuse to lay their eggs. I ob- 
tained an abundance of good milt, and to all appearances the 
eggs were ripe. Again and again was fertilization tried, but 
although the eggs were kept for four weeks they showed no 
signs of change except those that might be the effect of 
decomposition (see infra). A further difficulty was found in 
manipulation of the early stages of the eggs obtained from the 
natural nests, and many experiments were tried to ascertain 
the best method of procedure. For surface views a slight 
staining with osmic acid proved best, while for sections har- 
dening in successive grades of alcohol proved at least equal to 
chromic acid, Merkel's fluid, Perenyi's fluid, or corrosive sub- 
limate. The coagulation of the albumen by heat, so advan- 
tageous in studying many Arthropods, was here worthless. The 
greatest difficulty with the earlier stages was found in the 
extremely refractory chorion, which did not separate at all 
readily from the egg proper. I had in most cases to cut 
it and the egg together, and the results were far from 
satisfactory. 
The eggs were embedded in paraffin by chloroform, cut in 
ribbons, and fastened to the slide by the collodion method. 
They were then stained by eosin or haematoxylin. They did 
not readily take color, usually requiring ten minutes to stain 
with the former dye, which generally works much more quickly. 
My best results were with haematoxylin, overstaining, and then 
submersing in acid alcohol. 
' The eggs and embryos possess great vitality, living in con- 
finement with only the slightest care; and, as I write, I have 
specimens living which I obtained five months ago : they 
have spent the last three in a common saucer, the only atten- 
tion being to replace evaporation by ordinary hydrant water. 
The density of the water seems to have but little effect upon 
them, and I have had them live for several weeks in perfectly 
fresh water. This vitality, which is also characteristic of the 
adults, has an extremely interesting aspect when we consider 
the fact that Gigantostraca have an ancestry extending back 
to the Palaeozoic rocks. Professor E. S. Morse has noticed a 
