240 Professor Nuttall, Observations on Ticks, ete. 
Observations on Ticks: (a) Parthenogenesis, (b) Variation due 
to nutrition. By Professor NUTTALL. 
[Read 5 May 1913.] 
THE occurrence of parthenogenesis in ticks was recently 
observed by Aragéio, in Brazil, in a new species of Amblyomma 
(A. agamum), the males of which have not as yet been discovered. 
Three complete generations of this tick have been raised experi- 
mentally and thousands of females were brought to maturity in 
the absence of males. This constitutes the first record of partheno- 
genesis in ticks. 
The author described how he had succeeded in obtaiing a 
parthenogenetic offspring from Rhipicephalus bursa, a species 
(prevalent on sheep in countries bordering the Mediterranean) in 
which both sexes occur in fairly equal numbers upon the host. 
Larval ticks issued in limited numbers from the eggs laid by 
unfertilized females. 
Experiments were further recorded in which it was shown that 
the genus Rhipicephalus shows a considerable natural variation in 
size, and that imperfect feeding of the tick in its immature stages 
leads to the development of very small adults which, whilst fertile, 
are so different from the normal forms, that they could readily be 
taken for other species. It is only by determining the range of 
variability in a species under experimental conditions that the 
limits of a species in this respect can be determined and the 
making of bad species prevented. 
