Fes. 1909.] BOTANICAL SOCIETY OF EDINBURGH 27 
The worm is well adapted to its specific life conditions 
(1). Both sexes have a strong mouth-prick, swollen proxi- 
mally, by which the host’s tissues are pierced and fixation 
there effected. When not exserted the style lies in a buccal 
groove immediately behind which is situated a bulbous 
muscular gizzard. This sucks in the juices of the host. 
Marked sexual dimorphism occurs. The 2, which 
when adult is recognisable by its six-rayed chitinous cap or 
“calotte,” never loses its vermiform facies. But the 2, which 
undergoes one ecdysis less than the ~%, and in fact retains 
its larval skin when adult, is greatly changed after impreg- 
nation. The reproductive organs and the alimentary tract 
become enormously swollen. Ultimately the worm is lemon- 
or citron-shaped. The genital pore from being lateral is 
shifted to a distinctly terminal position. 
The larve of Heterodera are free living in the soil. At 
first they cannot be sexually distinguished. In some 
respects they resemble the adults, but differ in possessing 
pointed tails. After a time they attach themselves to the 
host plant, where the 2 remains for life, falling off in the 
end either as an empty skin or as a brood-chamber for the 
young. The ~ reaches maturity while attached to the 
plant. He then leaves it to find the 2. Just before leaving 
he has assumed his peculiar head-dress. The larva is 
destitute of it; so too is the 2, though in her case a 
covering of hardened sap simulates the “calotte” of the f. 
Within the body of the gravid 2 the embryos develop, 
and in their escape cause the death of their mother. The 
young may frequently be observed within a mucilaginous 
drop at the anal end of the parent. After hatching they 
make their way to the soil, where the life-cycle (four to 
five weeks) goes on as before. During the winter the un- 
hatched larvee of the last brood shelter in the skin of the 
dead mother. 
Heterodera schachtii, Schmdt., does not penetrate at all 
deeply into the tissues of the plants attacked. H. radici- 
cola, and the form of which we are now speaking, on the 
contrary, live embedded in the host. 
With respect to the former, the account of Vuillemin 
and Legrain (4) is here given without comment. These 
investigators found at El Oued (Sahara) that the majority 
