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Nematodirus filicollis Bud. 
Looss (1911) has shown that the mature larvae of Anchylostoma 
cast their protective skins as soon as they enter the body of their host, 
whether through the skin or through the mouth; he also showed that 
the completion of the second ecdysis can also take place in the open 
under certain artificial conditions. According to this investigator the 
process is always a purely mechanical one and is performed either 
actively by the larvae (e.g. under certain chemotactical stimuli when 
they unmistakably exert themselves to leave their envelopes) or passively 
(e.g. in certain media, such as gelatine or water containing numerous 
foreign particles, when the rending of the outer skin results from its 
mechanical retention by the medium whilst the larva itself attempts 
to move forwards). 
The larvae of Nematodirus are also able to complete their moults 
in the open at laboratory temperatures when subjected to certain 
conditions. Thus it was found that ecdysis occurred simultaneously in 
a number of ensheathed larvae living in a culture of faeces which had 
been repeatedly dried and remoistened during the course of some 
experiments on the resistance of the larvae to" drought. 
A similar phenomenon was observed on two' occasions in moist 
cultures of faeces which bad been attacked by fungi, and I was able 
to watch several individuals in the act of moulting. In these cases the 
hyphae of the fungus had enveloped the larvae and arrested their pro¬ 
gress, resulting in violent serpentine movements which finally led to 
the rupturing of the sheaths near the anterior extremities. 
On all occasions when the completion of the moult was observed in 
the Nematodirus larvae the process took place in a purely passive 
manner; I never succeeded in inducing active ecdysis by means of 
chemical stimidi, although the effects of various stains as well as of 
weak solutions of neutral salts, acids and alkalis were tried. 
The influence of temperature on the ensheathed larvae is, however, 
very marked, and repeated experiments showed that these when 
subjected to temperatures approximating to blood-temperature, with 
few exceptions, complete their ecdyses within a few hours. The 
experiments were performed by means of a small electric oven at a 
temperature of 38° C., the larvae being placed in small stoppered tubes 
in water and various solutions. The casting of the sheaths took place 
quite independently of the chemical composition of the fluid in 
which the larvae were kept, pure water as well as dilute neutral 
acid and alkaline solutions were used, always however with similar 
results. 
