i 2 6 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
In about seven days' time the egg becomes more ovoid, and, with a low 
power (a 3 objective ; No. 2 ocular ; Zeiss, stereoscopic), the hexapod larva 
can be seen to be forming within the translucent shell (PI. 1, fig. 2). At 
about the thirteenth day the egg-shell splits, nearly always posteriorly, 
in the sagittal plane. It measures at this moment 1. 03 by gmm. 
A hexapod larva (PL 1, fig. 4), which moves its legs but cannot 
crawl, may now be extracted from the shell. Normally the egg- 
case and its contents become batter, and the larva's skin wrinkled 
PL 1, fig. 7). Air enters beneath the egg-shell and the larval skin 
so that the young tick and his coverings form a dull, white disc. If the egg- 
shell be removed, it can be seen that the tick is about to moult. Its tegu- 
ment has split anteriorly, sometimes laterally, in the usual line of ecdysis 
at the junction of the dorsal and ventral surfaces ; and curled up within the 
hexapod larval skin can be seen the eight-legged nymph. When ecdysis 
finally takes place, the nymph throws off egg-shell and larval cast together. 
It usually emerges by getting out one of its hind legs first, and 
then, often turning around inside its casings, dragging its body out after. 
The measurements of ten nymphs taken just after leaving the shell were, 
average 1.02 by 0.87mm., the largest 1.10 by 0.96mm., the smallest 0.98 by 
0.8mm. 
The newly-hatched nymph (PL 1, fig. 8) has no genital pore, and the 
adult position of the stigmen is indicated by a small white spot and pit. Its 
capitulum is partially retractile, and is visible from above. Their bodies, under 
a low power, are translucent. Freshly-hatched nymphs usually do not feed at 
once. As a rule only three or four days later do they readily suck blood. 
From observations extending over two months, based .on ticks hatched in 
the laboratory from infected parents, but fed upon uninfected animals, it 
seems that if food is plentiful a young tick grows rapidly. The intervals 
between the moults seem to vary very considerably ; but in the two months 
after it leaves the shell the tick may moult three times and come to measure, 
roughly, 5 by 2.5mm. If food is lacking, growth is much less rapid. 
A full-grown female, filled with eggs and blood, may measure 12 by 10 
by 7mm. After the nymphs first moult the stigmen is easily distinguishable, 
but the genital pore is still absent. The measurement of twenty young ticks 
at this stage gave, average 1.47 by 1.22mm., largest 1.92 by 1.37mm., the 
smallest 1.34 by 1.07mm. It is only after the second moult that the sexual 
pore is seen as a very slight depression in the middle line of the ventral sur- 
face on a level with the bases of ihe first pair of legs. Cleavage of the skin 
for ecdysis always takes place along the line indicated in the diagram 
(PL 3, fig. 3). The split usually commences anteriorly. The feet and 
ventral surfaces are first freed, then the dorsum, and the perfect cast is left. 
Either dorsal or ventral half of the moult may, however, remain attached 
after the other moiety has been thrown off. 
It is impossible to say how long the ticks live, or for how long they 
remain infective. Ticks caught on October 24, and kept without food, are 
still alive, and have freely reproduced. Ticks caught before November 23, 
still alive (March 28, 1905), and have freely reproduced. Ticks caught before 
November 23, at Nywange, and kept without food, were able to infect a 
monkey with spirochaetes if months later. 
