*256 
Liver Rot of Sheep 
days with one straight dry spell of 10 days. In this Area all winters 
are sufficiently wet to allow L. truncatula to reach breeding size by spring, 
and it is wet summers that lead up to an outbreak of rot; while a drought 
in the spring will, in particular, assist in limiting its spread. One may 
say that the rainfall recorded for any particular year bears a very close 
relation to the number of rainy days. The number of rainy days, as 
has been stated, is fairly constant throughout the whole Area for any 
individual year, and it might be suggested that the Area is of such a 
character that droughts also are coincident. This means that no one 
district of the Area can act as a natural reservoir against paucity of 
L. truncatula in other districts, except in one district where suitable 
physical environment and a high rainfall coincide: there rot is endemic. 
Sequence of Life History. 
The general sequence of the life history of L. truncatula for 1915-16 
was, as far as I could ascertain, as follows (all manner of variations of 
course occur, governed by environmental differences). 
1915. November. Ditches refilled from direct rainfall or from springs recommenc¬ 
ing to flow. 
1915. December. Hatching of those ova surviving the drought period. 
1916. January. 
1916. February. 
1916. March. All survivors of former generations and those of the new generations 
to attain 5 mm. in length (or thereabouts) commence to deposit ova. 
1916. April. Deposition of ova continues as maturity is reached. Hatching of 
ova first deposited (after 6 weeks). 
1916. May. Hatching continues. 
1916. June (mid). First young snails of the year reach maturity and commence 
to deposit ova. 
1916. July. Second generation of the year hatch (unless dried up). 
1916. August. Dry, except in very favourable situations. 
1916. September. Wet in early part, some ditches refilling. 
Should drought not interfere, possibly a third generation would 
result, since ova deposited at the end of June should hatch by the end 
of July, become adult during September, and deposit ova in October. 
This sequence has not been observed since during eacli year of the Survey 
there have been prolonged droughts, and until 1916, the 2nd generation 
was only once noted (July 1915, without the Area). It should be 
possible, however, given suitable conditions, for three generations of 
snails to complete their growth in a year; allowing 17 weeks per genera¬ 
tion. 
