452 
Journal o f Agricultural Research 
Vol. XXIX, No. 9 
to , 80° F.) and examinations were 
made by mounting the glass vessels 
containing liquid media directly on the 
stage of the microscope for general ob¬ 
servation, and resorting to isolation of 
larvae whenever detailed observations 
on structure or behavior were desirable. 
Inasmuch as not all eggs hatch at the 
same time, because of variation in rate 
of development and various other fac¬ 
tors, newly hatched larvae were isolated 
and mounted on cover glasses inverted 
over hollow ground slides or over ordi¬ 
nary slides to which temporary cham¬ 
bers were sealed. Thus the changes 
undergone by the larvae could be fol¬ 
lowed very readily without such con¬ 
fusion as would result from having 
larvae at various stages of development 
in the same dish. If precautions are 
taken to secure good-sized drops, and 
if hanging-drop preparations are prop¬ 
erly sealed, the changes in the larvae 
from the time of hatching to the in¬ 
fective stage may be followed without 
adding additional fluid, thus avoiding 
the need of removing the cover glass 
at various intervals. In one series of 
observations eggs and larvae were se¬ 
cured from day to day from solid cul¬ 
ture media and their development was 
compared with that of eggs and larvae 
in liquid media. No noteworthy differ¬ 
ences in rapidity of development were 
found; therefore observation on the 
rapidity of development in subsequent 
series of cultures was limited to those 
made on liquid media. 
DESCRIPTION OF THE EGG 
The egg of Bustomum phlebotomum , 
in common with eggs of other stron- 
gyles, is thin-shelled, elliptical in 
shape, and exhibits considerable range 
in size (52 to 106 m in length, by 43 to 
60 m in width). In a series of measure¬ 
ments involving more than 100 eggs 
only 10 per cent of the eggs exceeded a 
length of 100 n and only about 5 
per cent were shorter than 75 ix. The 
majority of eggs measured were from 
85 to 95 fx long and slightly over 50 m 
wide. No definite correlation was 
found between length and width of 
eggs. Some long eggs are compar¬ 
atively narrow and some present an 
almost spherical appearance. 
DEVELOPMENT OF THE EGG 
Conradi and Barnett U) state that 
before the egg is passed from the body 
of the host it is in the 
mulberry stage. These 
writers also note that 
partial incubation of the 
egg in the intestine of 
the host seems to be im¬ 
portant, since eggs that 
were taken from the host's 
intestine and thus missed 
the partial incubation pe¬ 
riod in the intestine 
showed a heavier mortal¬ 
ity than eggs collected 
from feces. The present 
writer noted that eggs be¬ 
gin to segment in the 
uterus of the female para¬ 
site, as shown in Figure 
1. Eggs obtained as a re¬ 
sult of chopping freshly 
collected worms are in the 
one-, two-, and four-cell 
stages, and rarely in the 
eight-cell stage. At room 
temperature (70° to 80° 
F.) the development of such eggs takes 
place rather slowly. After 24 hours of 
incubation it was noted that compara¬ 
tively few eggs had reached the mul¬ 
berry stage; and after 72 hours of 
incubation comparatively few embry- 
onated eggs, with embryos moving in 
the shells, were found. Ninety-six- 
hour cultures usually showed free larvae 
as well as embryonated eggs, the latter 
hatching in the course of a few hours. 
According to Conradi and Barnett (4), 
at a temperature of 48° to 60° it requir¬ 
ed 31 days for the eggs to hatch. These 
writers also report that eggs obtained 
from feces on February 26 hatched on 
February 28; but they do not give the 
temperature at which the eggs were 
incubated. According to observations 
by the present writer, eggs at various 
stages of development undergo disin¬ 
tegration in culture media not only 
because of the presence of bacteria in 
Fig. 1.—Portion of uterus containing segmented eggs 
