Artificial Partheuodcnesis in Ticls 
4()() 
The 64 larvae, progeny of $ 1, were placed on a ram 23 days after they 
emerged, and the 90 larvae, progeny of $11, were placed on a ram 60 
days after they emerged, but in neither case were any recovered gorged. 
These observations show a marked contrast in the behaviour of 
fertilized and unfertilized females. Whereas all females placed with 
males upon the host dropped off gorged in 4-12 days (minimum and 
maximum periods), females in the absence of males remained upon the 
host for 15-38 days (Experiment 2) or 25-91 days (Experiment 1). 
Even after this long period of feeding, none of the unfertilized females 
became nearly as fully gorged as those which had been fertilized. Owing 
to the different temperature conditions under which the unfertilized 
and fertilized females were maintained (30° and 18-24° C. respectively), 
the duration of the pre-oviposition and oviposition periods cannot be 
compared. In the unfertilized females, all of which were maintained 
at 30° C., oviposition began after 4-9 days (Experiment 1) or 3-19 days 
(Experiment 2), the process lasting 9-17 days (Experiment 1) or 5-14 
days (Experiment 2); the period of egg-laying might be equally short¬ 
ened in fertilized females maintained at 30° C. Whereas 10 fertilized 
females laid roundly 4960-6890 eggs apiece, the 10 unfertilized females 
in our two experiments laid respectively 12, 100, 500, 676, 1008, 1680, 
1990, 2160, 2340, and 4830 eggs apiece. Whilst only 2 out of 29 females 
to which males had had access died without ovipositing, of the unfer¬ 
tilized females there died 13 out of 19 (in Experiment 1) and 16 out of 
40 (in Experiment 2) without ovipositing. 
In my short note on parthenogenesis in ticks, to which reference has 
been made, it was stated that it was observed in R. bursa. I laboured 
under the impression that it was a normal though perhaps rare occur¬ 
rence, but I am now convinced, as a result of repeating the experiment, 
that the 'parthenogenesis observed was artificially induced by the tnanipu- 
lations accompanying the enumeration of the eggs. 
The method devised by me for enumerating the eggs laid by ticks 
is described in Part I [Parasitology, vi, pp. 73-74): “When enumerating 
by this method, we separate the eggs composing the mass by immersing 
them in nor^nal salt solution and rubbing them about gently with the aid 
of a earners hair brush”. . .etc. (not italicised in the original). 
In the protocol of Experiment 1 it is stated that the eggs of four 
unfertilized $s were enumerated, and that the larvae emerged from three 
out of the four batches of eggs as follows: 
