EELWORM ‘‘ ONION-SICKNESS.”’ 109 
The Plate* opposite gives figures of 7. devastatrir, including 
male and female Eelworms taken from Onions, in each case magnified 
200 times; and also the anterior portion of another of the same 
species, also taken from an Onion, and magnified 440 times. The 
figures are copied from the work mentioned below by kind permission 
of Dr. Ritzema Bos,+ with his explanations as below. 
In reply to my enquiries, Mr. Pratt kindly furnished me with some 
observations pointing strongly to this infestation being propagated or 
spread, just in the same manner with the Onions that it is with Oats 
or Clover, by infested plants being thrown to the manure heap, from 
which the Eelworms are carried back to the garden ground or field. 
And besides this (with Onions), seed from infested plants may very 
* EXPLANATION OF Piate.—Fic.1. Tylenchus devastatrixz, female, taken from 
an Onion plant; magnified 200 times. 
a, spear; 0, first muscular swelling of the esophagus; c, second csophageal 
ring; d, e, intestine, properly so called; e, f, rectum; f, anal opening; g, excretory 
pore (orifice of the lateral vessel); h, commencement of the ovary; i, ovule, with 
nuclei (or germs), not fertilised; k, first half of the oviduct (tube), with sperma- 
tozoids; 1, second half of the oviduct, with glands in the wall; m, anterior portion 
of the uterus, containing a fertilised egg; n, sac, with closed extremity, second 
portion of uterus; 0, vulva. 
Fic. 2. Tylenchus devastatriz, male, taken from an Onion plant; magnified 
200 times. 
For a, b, c, d, e, and g, see explanation of preceding figure; f, cloacal opening ; 
h, commencement of the testis; i, mother-cells of the spermatozoids (Spermato- 
blastes) ; k, cells further divided, forming spermatozoids; 1, vas deferens; m, spicule; 
n, accessory piece ; 0, purse. 
Fie. 3. Anterior portion of a Tylenchus devastatriz, not fully developed, taken 
from an Onion plant; magnified 440 times. 
For a, b, c, and d, see explanation of fig. 1. In front of the spear (a) is shown 
the labial region, and lower, at the base of the spear, the musculi protractorii leading 
forwards, and the musculi retractorii leading backwards. The half of the esophagus 
in advance of the first bulb, or muscular swelling (b), has a straight direction; the 
half which extends from the first to the second muscular swelling is waved. In the 
second bulb nuclei are visible. Near (d) the intestine begins; in the wall of this 
the separate cells are not distinguishable, because of the presence of the numerous 
drops, which refract the light strongly. 
Fic. 4, Anterior portion of a Tylenchus devastatrix, taken from a Wheat plant; 
magnified 440 times. 
Fic. 5. Eelworms from Hyacinth, dried and rolled together. 
Fies.6 and 7. Eggs of T. devastatriz, showing an early and late stage of 
formation of the embryo. 
Fic. 8. The young wormlet (T. devastatriz) newly emerged from the egg. 
Fic. 9. Egg of T. devastatriz before segmentation of protoplasm. 
The figures on the Plate are all greatly magnified. The life size of the male and 
female is 1:5 mm., that is, a little more than the twenty-fifth part of an inch. 
+ See Plates I. and II. in ‘ L’Anguillule de la Tige (Tylenchus devastatriz, 
Kuhn),’ par Dr. J. Ritzema Bos, Professeur 4 l’Institut Agricole de I’Etat a 
Wageningen (now Director of the Phytopathological Laboratory at Amsterdam), 
