54 
L. Kaufman: 
of leaves and resemble rather thick thread. In the black axolotl 
we observe under the magnifying glass an aggregation of large 
formless clots of pigment, especially along the vessels. During the 
period of rapid loss of weight of axolotls fed on thyroidine, gills 
undergo intense degeneration. During the period of increasing and 
of stationary weight, which lasts from 10 to 12 days, changes in 
the gills are small; yet during the 8 to 14 days of rapid emacia¬ 
tion, the gills become reduced to short fragments of gill-trunks. 
In the microscopical dissection of a gill-trunk, we observe consi¬ 
derable changes, especially in their muscles which lose their trans¬ 
verse striation and are split into a series of longitudinal fibres. 
Ley dig’s cells in the epithelium undergo degeneration. The con¬ 
nective tissue is the last to lose its normal appearance. 
Under the influence of thyroidine-food, the breadth of the gill- 
filament is considerably reduced. Fig. 5 represents the dissection 
of a normal gill-filament, and fig. 6 the dissection of a filament 
in the first stages of degeneration; both figures are drawn to the 
same scale. We see that the breadth of the gill has decreased by 
one-half. The diameter of the large blood-vessel is here only 70 
Capillary vessels lie directly under the epithelium. In the con¬ 
nective tissue, which is more abundant than in the normal state, 
blood-corpuscles often appear lying outside the vessels, and clots 
of pigment irregularly dispersed. The epithelium is now com¬ 
posed of extremely flat and long cells. The number of layers is 
frequently reduced to one. At this stage the wall of the blood¬ 
vessels, together with the epithelium, forms a narrow string of 
tissue. On fig. 7 we see part of the dissected wall of the epithelium 
of a normal gill-filament; comparison with fig. 8, representing an 
analogous dissection of a filament of an axolotl, fed on thyroidine- 
tabloids four times during 11 days, shows that the thickness of 
the wall as well as that of the epithelium has considerably decreas¬ 
ed. The cellular borders disappear, the plasma is dissolved. Here 
and there, the epithelium is shed off and the wall of the vessel 
bursts. During the rapid resorption of the filament, its dissection 
represents a formless mass of turbid plasma and of nuclei under¬ 
going chromatolysis. 
Since the blood-vessels of the gills still contain blood in advanced 
stages of degeneration, the supposition arises that during metamor¬ 
phosis blood not only gives no nourishment to the tissues of the 
