ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
701 
C2) Preparing- Objects. 
Development of Limax.* — Mr. C. A. Kofoid, in his study of the 
development of Limax, found the following the most successful method 
for keeping the animals in captivity. A tin box with proper ventilation 
is filled to the depth of one inch with clean sand, which forms a suitable 
substratum for the retention of moisture. On this is laid a sheet of 
moss, to whose under surface the earth still adheres. The leaves of the 
common plantain furnish acceptable food, and when this is no longer 
available, fresh cabbage leaves and apple parings can be used. During 
the first week of captivity, the slugs furnish eggs in great abundance, 
but after that time the number diminishes and the quality deteriorates 
so rapidly that it is imperative that a new colony be secured. Abnor- 
malities in the living egg show themselves in the early stages by a loose 
assemblage of the cells, and the increasing opacity of the embryo. 
Before hardening the embryo, it is necessary to free it from the envelopes 
and albumen which surround it. By inserting two fine cambric needles 
in one holder, so that the distance between the points is less than the 
diameter of the unshelled egg, it is possible to hold the egg between 
these two needles and pierce it by a third. A quick shear-like cut with 
the third needle against one of the other two tears open one side of the 
egg, and allows the albumen and the ovum to escape from the envelopes. 
As the albumen interferes with section-cutting, and obscures whole pre- 
parations, it must be removed entirely. This for a long time presented 
a most serious obstacle to the author’s work. Washing off the albumen 
with water is a very slow and tedious process, and not always successful. 
Hypochlorite of soda may indeed be used, but the difficulty of using this 
lies in the necessity of stopping the action of the hypochlorite before it 
attacks the ovum. It does indeed free the eggs from the albumen, and 
does not interfere with staining, but the proportion of eggs destroyed in 
the process is very great. The method which gave the best results was 
the following. The living eggs are placed in normal salt solution 
(0*75 per cent.), in which they are at once shelled. They are then 
freed from the albumen by washing them in the salt solution, which is 
dropped upon them from a pipette. The operation is carried on in 
large glass dishes resembling watch-glasses, but provided with flat 
polished bottoms, which are placed upon a black tile ; this renders the 
eggs visible to the naked eye. The salt solution dissolves away the 
albumen, leaving the egg entirely free. It can then be transferred to 
any desired killing reagent by the use of a capillary glass tube. It is 
well to shorten the exposure in the salt solution as much as possible, 
for nuclear conditions are somewhat altered by its action. Eggs which 
are laid in it for ten minutes have their nuclear membranes much dis- 
tended, and the chromatin gathered into a homogeneous mass in the 
centre of the nucleus, surrounded by a clear region of nuclear sap. 
Excellent results were obtained by subjecting the eggs to the action of 
Fol’s modification of Flemming’s mixture for one minute, and then 
transferring them at once to Orth’s picro-carminate of lithium. Rapid 
decolorisation with 90 per cent, alcohol plus 5 per cent, hydrochloric 
acid gave very good results. The eggs were studied in the clearing 
* Bull. Mus. Comp. Zool., xxvii. (1895) pp. 37-40. 
