with Report on Experiments. 
373 
moulting here illustrated is the second that occurs in the 
parasite's lifetime. Whether it be so or not, the phenomenon 
is sufficiently striking. The moulting worm shows the old skin, 
forming a sort of loose sac which completely invests the new skin, 
leaving a large space between the lower end of the body and the 
point of the original tail. The shape of the now more or less 
metamorphosed larva becomes altered, the blunted form of its 
new tail being the most conspicuous feature. After a while 
traces of the internal reproductive organs make their appearance ; 
and one may soon discern a little sheath containing rudiments 
of the male spicules, as well as the commencing tube of the testis 
and vas deferens. The larva figured in this interesting stage 
of growth measured of an inch from head to tail, over all ; 
its enclosed and partly metamorphosed larva being shorter, or 
about of an inch. 
Characters of the Free Larvie. — After the lapse of an interval 
of twenty-four hours from the time at which the metamorphosing 
larva was sketched (as above), I again captured the worm. Its 
ecdysis was now complete ; not a trace of the old skin remained. 
Its sexual distinctiveness had become more pronounced, the 
two short and stout spicules being particularly well defined. 
Already, also, the tail end displayed lateral expansions of the 
new skin, forming the rudiment of a hood, which presented a 
wavy margin with crenelations due to the presence and support 
of five pairs of regularly-arranged rays. The tail itself ended 
in a minute awl-shaped projection. This specimen was in the 
condition here drawn (Fig. 10). It must be added that the 
now more fully-developed vas deferens and testis had pushed 
aside the mid-gut, the outer surface of the reproductive gland 
being dotted with polygonal, nucleated cells. The digestive 
tube itself had become more strongly marked, its walls being 
thickened by six-sided gastric gland-cells, of which there 
appeared to be a double row. The lumen of the mid-gut 
was indicated by a central dark line, but the hind-gut or 
rectum was somewhat obscured by other organs. The fore- 
gut had become very conspicuous, the chitin bands of the 
oral cup, the oesophageal tube and the bulb being all well 
marked. 
A new Expei'iment. — One by one the few larvae that I had 
reared on the fern-fronds were either dying or disappearing, 
so that by the 1st of November I had only a solitary larva left. 
This worm continued to grow rapidly, but its internal organs 
were not materially advanced in complexity. Wishing to 
obtain further results, I sought to place the larva under new 
conditions. Of course, to transfer it to the windpipe of a 
living calf would have given the larva a good chance of rapidly 
