220 
Journal of Agricultural Research 
Vol. II, No. 3 
the development of the male of Tylenchulus is of a somewhat peculiar 
character, in that as it increases in age, it may decrease somewhat in size, 
and that the oral spear, so characteristic a mark of the group of genera 
to which Tylenchulus belongs, deteriorates so 
markedly in this instance that adult males are 
sometimes found that appear to have no trace 
whatever of this organ. In all cases it deterio¬ 
rates so much as to fade into an inconspicuous 
feature of the anatomy (fig. 4). It is somewhat 
doubtful whether the males enter the unimpaired 
tissues of Citrus roots. In fact, most of the evi¬ 
dence appears to point the other way and seems 
to indicate that they seldom, if ever, enter sound 
roots. The males mature rapidly, and there is 
some doubt whether they feed at all; for, as 
already stated, instead of increasing in size as 
they grow older, they decrease and become more 
slender. Theyare probably ill-fitted to bore their 
way into the tissues of Citrus roots, lacking, as 
they apparently do, an efficient puncturing or¬ 
gan. All specimens of Tylenchulus seen by the 
writer to be embedded in comparatively sound 
roots have proved to be females, though it is 
entirely possible that an examination of a larger 
number of cases might prove that males also em¬ 
bed themselves. 
The eggs of Tylenchulus semipeneirans are 
of comparatively large size, thin-shelled, and 
usually are not deposited until after segmen¬ 
tation begins. Their size is such that the ute¬ 
rus of the adult female commonly contains only 
one or two at a time (figs. 1 and 5); and, as 
a rule, these are found in the early stages of 
segmentation, sometimes containing only one 
blastomere, sometimes two, sometimes three, 
occasionally as many as a dozen. The exact 
length of time the eggs remain in the uterus 
is at present unknown, but under favorable 
conditions does not exceed a few days. They 
are deposited one at a time in batches of a 
dozen to a score or more and are sometimes 
found encased in a somewhat indefinite mass of “gummy" matter. 
Judging from the experiments, these eggs hatch very promptly, prob¬ 
ably within a day or two after being deposited, and produce colorless 
Fig. 4. —Tylenchulus semipenetrgns: 
Lateral view of full-grown male. 
The spear is usually very incon¬ 
spicuous —always deteriorated. 
Note also the deteriorated me¬ 
dian bulb, sometimes apparently 
absent. In the male, in contrast 
with the female, the anus devel¬ 
ops. a , Lip region; 6, spear; c, 
3-bulbed base of spear; d t oeso¬ 
phageal lumen; e, median oeso¬ 
phageal bulb; /, nerve ring; g , car¬ 
diac oesophageal bulb; A, begin¬ 
ning of the intestine; j, large intes¬ 
tinal granule; k y small intestinal 
granule; anus; m, spicula; 
excretory pore; o, spermatocyte; 
p, vas deferens; g, spermatozoon. 
