EDUARD UHLENHUTH 327 



discussed it in a previous article,^ that the larvae of all species so far 

 examined must grow longer in low temperature than in high tempera- 

 ture before metamorphosis can take place, without, however, under- 

 these circumstances becoming neotenous. Unfortunately Kammerer 

 does not mention at what temperatures his larvae were kept. In the 

 same article Kammerer refers to neotenous larvae of Salamandra 

 maculosa, 2 years old; it is very probable that these larvae were truly 

 neotenous. The experiments reported in this paper make it, however, 

 very doubtful that this result could have been obtained by merely 

 cutting off the limbs and the tails. I tested the effect of the removal 

 of the limbs and of the tail followed by regeneration of these parts 

 first in the species Amby stoma opacum. In the fall of 1916 the eggs 

 of one female were collected and twenty-eight of them divided into 

 four series; two series (E and G), consisting of six larvae each, were 

 used as experimental series, E being kept at approximately 25°C., 

 G at approximately 15°C.; each experimental series was controlled 

 by a series consisting of eight animals (A and C). The larvae were 

 measured and examined at least once every week. They were kept 

 in individual jars, and individual records were made. Both fore limbs 

 were removed from the larvae of Series E and G 46 days after hatching, 

 and 88 days after hatching 50 per cent of the tail was cut off. In 

 Series E the regeneration of the legs was nearly completed 102 days 

 after hatching, i.e. 80 days before metamorphosis; in Series G the legs 

 had not regenerated to their normal length 109 days after hatching, 

 but from this time on regeneration occurred at a very slow rate, and 

 the animals never possessed legs of normal length. Regeneration of 

 the tails was most vigorous during the first weeks after they had been 

 cut off but continued in both series throughout the larval period. 



Table I shows the result of this experiment. For reasons discussed 

 in other papers,^ metamorphosis was regarded as taking place at the 

 time when the first molt occurred ; consequently the figures recorded 

 in this table represent the number of days after which the animals 

 shed their skins for the first time. In several larvae this figure was not 

 recorded, the date when they were set on land being recorded instead. 

 At 25°C. this was done on the same day as the first molt, or 1 day 



' Uhlenhuth, E., /. Gen. Physiol., 1918-19, i, 525. 



