1895]. Microscopy. 89 
Plethodon placed in a 4 per cent. solution of formaldehyde (10 per 
cent. of the commercial formalin) were soon killed, and on the day fol- 
lowing the immersion were thoroughly hardened and after a week or so 
have not shrunken noticeably further than that the costal furrows are 
a little more strongly marked than in life. The reddish coloring of one 
of them is fully as fresh as when the animal was caught. A tree-frog 
placed in the same solution at the same time became somewhat swollen, 
but by cutting the skin in the abdominal region, the swelling was then 
shown to be due to an entrance of the fluid into the subdermal space 
as pointed out by Blum.- The swollen tongue, which protruded from 
the mouth a little, would indicate, however, that there had been a 
swelling of some of the tissues. The same swelling of the head was 
noticed in the salamanders, but with them it is not so marked. 
A single adult Amblystoma punctatum, that had been first anesthe- 
tized with chloroform, was placed in a solution equivalent to about 1 
per cent. of formaldehyde, and was found to harden rapidly. There 
was, however, a very noticeable swelling of the whole body within 
twenty-four hours, while, at the same time, the costal furrows, as in 
the Plethodon specimens, became more marked. After about a week’s 
immersion in the 1 per cent. solution, it was found that the bright 
orange-yellow spots of the live animal had very noticeably faded to 
light yellow. The specimen was then changed to a 4 per cent. solution 
and after an equal length of time the fading appeared to have gone no 
further, while the swelling was somewhat reduced. As it is the speci- 
men is much better preserved than it would have been in alcohol. 
Earthworms and the Arthropods were tried in all solutions. The 
former swell but slightly in the weaker solutions and contract very 
much less in the stronger ones than they would in alcohol, chromic 
acid or the other hardening agents. They harden in a } per cent. 
solution as well as in the stronger ones or in pure formalin, the differ- 
ence being one of time. In the Arthropods—sow-bugs and myriapods 
—the fluid in some of the experiments entered the body to such an 
extent as to stretch the animals out, leaving broad gaps between the 
harder parts of the segments. This stretching or swelling was first 
seen in the specimens in the J and 2 per cent. solutions, but sometime 
later those in all the solutions below 1 per cent. were fully as badly 
swollen, if not more so. Besides this the brownish colors of the animals 
became more faint, while the fluid became very much colored. This 
extraction of color is most noticeable with the } per cent. solution. 
Slugs placed in }, 3, 3, 1, 2, 4, 8, 10 and 20 per cent. solutions seem 
equally well preserved. In the 1 and2 per cent. solutions the head is _ 
