C. L. Walton 
259 
leduced but the data for this last statement are not so complete and are 
mainly obtained from field observations some details of which will now 
be given. 
Field Observations upon the Life History. 
While there is no doubt in my mind as to the facts deducible from 
the field observations, it has proved difficult to carry out the necessary 
controlled Laboratory check experiments when hatching is delayed for 
considerable periods, time, water and diseases of the ova being the chief 
troubles. As regards the first, much of my time was taken by field 
work, and duties as 2nd Lieut, with the University O.T.C. Finally, while 
controlled experiments attempted in a suitable stream near Aberystwyth 
on a small scale were fairly successful in 1915, an elaborate series arranged 
in the spring of 1916 were twice destroyed by most unusual floods. 
The effects of meteorological and other conditions upon the life 
histories of L. truncatula and L. peregra will be best illustrated by follow¬ 
ing the sequence of events in one of the localities kept under more or 
less constant observation. 
That about to be described is a streamlet situated some three miles 
from Aberystwyth, two from the coast, and flowing • gently in a s.e. 
direction from the 100 feet contour line for a distance of some 200 yards 
down to a small muddy pool. This streamlet occupies a very shallow 
ditch at the foot of a bank, bordering the eastern side of a wide well 
kept farm road, and lies open to the sun. It is fed by springs rising 
in the sloping grass fields above, the sub-soil of which is glacial clay 
and detritus. The road is but little used for traffic, but a large herd of 
cows passes and re-passes constantly between farm and pasture, and 
these drink at the pool above mentioned and graze about and trample 
the ditch to a considerable extent. Sheep also are grazed in the fields 
from which the stream receives its supply of water and at the time of 
my first observation Liver Rot was present among them to some extent, 
not obtained from this ditch, but in all probability from the infected 
district from which they came (some 10 miles distant). It is also to be 
noted that rabbits are abundant near by, but I have no record of infected 
livers among them. Neither ducks nor fowls reach either pond or 
stream. The streamlet flows but slowly in its upper part and there 
contains a good deal of Poa fluitans, the slope being steeper, there 
follows a somewhat swifter portion and finally, near the pool, the flow 
is again slower and there is more mud. On March 27th, 1914, truncatula 
was of fair size and abundance in the upper portion, together with a 
