5 
The decapitated larva of this stage when mechanically stimulated 
shows the same reaction as the normal. The contractions of the 
myotomes begin in the same locality and proceed slowly to the level 
of the posterior limb bud. The decapitated larva shows the same 
lateral movements of the tail, but at less frequent intervals. It is at 
this time scarcely able to gain the upright position and the periods 
of repose are much longer. The efforts on the part of the .larva to 
maintain an upright position although feeble, are positive. 
Larvae 20-21 mm. The normal larva while now able to main- 
tain an upright position is unable to swim freely because of the 
heavy yolk. Through a series of rapid lateral movements of the tail 
it is able to move along over the bottom of the aquarium. Occa- 
sionally one is observed to lift the yolk from the bottom of the aquarium, 
but at most momentarily. The legs are as yet not long enough to be 
of aid in moving. The tail is the organ of locomotion. 
The decapitated larvae are for the most part unable to maintain 
an upright position. Yet now and then one obtains and maintains 
this position for some time. They rarely move about unless mechani- 
cally stimulated and even when thus stimulated they move but short 
distance. In this movement, as in the normal, the tail serves as the 
organ of locomotion. 
Larvae 24-25 mm. The larva is now very active and moves 
about the aquarium both by swimming and crawling. In the latter 
movement the anterior limbs are used, but the posterior are not far 
enough differentiated to be of use. When undisturbed it crawls about 
slowly always seeking the darker places in the aquarium. If, however, 
the larva be disturbed, the Jegs remain motionless and the powerful 
tail serves as the sole means of locomotion. When sheltering objects 
are present, it endeavors to conceal itself beneath them. The gills 
stand out prominently on either side, but no amount of stimulation 
will cause them to retract, whereas in the later stages the slightest 
disturbances of the water causes them to quickly contract. 
The decapitated larva uses its anterior limbs in crawling and 
the tail in propelling. They too invariably seek the sheltering objects 
and the darker places in the aquarium. The gills are well diffe- 
rentiated, but are never retracted. The movements are not quite as 
well defined as those of the normal and are less frequent. 
Larvae 29-30 mm. The larva of 30 mm. walks slowly from 
place to place when undisturbed. In this movement, the anterior 
