yar eel 
1883. ] Microscopy. 1205 
stance, causes the cells, all through the cleavage stages as well as 
the later embryonic stages, to swell and in many cases to become 
completely disorganized. The embryonic stages can be hardened 
in chromic acid (one per cent), but the yelk contracts considera- 
bly without becoming well hardened even after three days’ im- 
mersion. 
All sorts of wrinkles and distortions are caused when the ova 
are transferred from the acid to alcohol. My best results have 
been obtained with osmic acid and a modified form of Meckel’s 
fluid. This fluid, as used by Dr. Eisig, consists of chromic acid 
(1% per cent) and platinum chloride (34 per cent) mixed in equal 
parts. Thus prepared it causes maceration of the embryonic por- 
tion of the egg. By using a stronger chromic acid (1 per cent) 
and combining it as before with the same quantity of platinum 
chloride (1/ per cent), everything may be well preserved and har- 
dened except the yelk. Before transferring to alcohol, after one 
to two days’ immersion in this fluid, it is necessary to prick the 
egg membrane in order that the alcohol may reach the egg 
readily, otherwise the membrane wrinkles badly and often injures 
the embryo ; 
For the cleavage stages this fluid cannot be used with success 
unless the egg has been first killed by another agent; for eggs 
placed in this fluid continue to live for a considerable time, and 
may even pass through one or two stages of cleavage. ; 
therefore necessary to use some agent that kills almost instantly. 
: e 
left for twenty-four hours or more. This fluid not only arrests 
the process of blackening, but actually bleaches the egg. 
After this treatment it is an easy matter to separate the blasto- 
derm from the yelk by needles, and the preparations thus 0 
‘ined can be mounted 27 foto, or sectioned. As the blastoderm 
's quite thin during the cleavage stages, a whole series of these 
es may be mounted and studied from the surface to adro 
tage. After removal from the acid the preparations may 5 
a at once, and then treated with alcohol and mounted in 
sam. 
Moror Nerve Enpines—Ciaccio! has investigated a apol 
nerve-plates in the depressor muscle of the jaws of Torpeao ™ 
thick ér i ; ips were then left for five 
cut with scissors, the strips w in distilled water 
Minutes in fresh filtered lemon juice, washed 
1 
Arch, Ital. Biok, 111, 75. 
