172 
CHARLES L. PARMENTER 
The living larvae were thrown into Flemming’s stronger solu¬ 
tion. After about four hours of fixation, the tails were split 
dorsoventrally 2 into two thin plates of cells. These two plates 
of cells were then fixed twenty hours longer. After washing 
in running tap-water for twelve hours or more, the pieces were 
stained in toto in Heidenhain’s haematoxylin, carefully dehy¬ 
drated, and cleared in xylol and mounted in damar. 
Gill-plate epithelium 
The most successful gill-plate preparations were also obtained 
from larvae f to If inches long. In each larva there are eight 
gill plates, one subtended from each gill arch and another behind 
each posterior gill cleft. These gill plates contain very numer¬ 
ous mitotic figures. They are composed of two epithelial 
lamellae with connective-tissue cells and capillaries lying between 
them. The two layers, unseparated, are so thin that they give 
very excellent preparations. 
The material was fixed in situ by dropping the living larvae 
into the Flemming’s stronger solution as soon as they were taken 
from the net. They were fixed in situ twenty-four hours and 
2 Haecker (’99) describes a very successful method of separating these two plates 
of cells. The posterior end of the larva is cut off after fixation just in front of 
the cloaca. With a sharp scalpel the thick cephalic end of the tail is split dorso¬ 
ventrally through the middle of the vertebra to a depth of an eighth of an inch 
or more. By grasping with the forceps the ends thus made free, the two layers 
of epithelium can be pulled apart in a manner similar to separating two sheets 
of fly-paper with adhesive surfaces sticking together. Professor Sigerfoos advises 
separating the two layers after about four hours of fixation and then allowing to 
fix about twenty hours longer. 
The numerous large mitotic figures in various stages with clear cell walls 
which can be studied without an immersion lens makes this material excellent 
for the class-room. The gill-plate preparations are equal or superior to those 
of the tail epithelium. Those of larger larvae are too thick when mounted in 
toto, but give very satisfactory preparations when separated. Peritoneal prepa¬ 
rations of larger larvae contain fewer mitoses and the cell walls are indistinct. 
However, preparations can be made from the more rapidly growing shorter 
larvae from which the gill-plates were taken and would probably contain more 
divisions. Preparations of Ambystoma punctatum are less favorable than those 
of A. tigrinum because there are fewer figures, more pigment cells in the tail 
epithelium and the gill-plates are small and thicker. 
