50 EELWORMS. 



two species of Heterodera are not eel-shaped, are very important to be 

 borne in mind, and those who have to depend on others for identifi- 

 cation would do well to ask to have this point well examined into, 

 otherwise mistakes, which are very important practically, sometimes 

 occur, and loss and disappointment is likely to arise from want of the 

 proper treatment. 



The Tylenchus devastatriv, or " Stem Eelworm," is the kind which 

 as yet has been most commonly observed in this country ; but as the 

 observations of the past few years have shown that the Heterodera 

 radicicola is also present in the country, and the observations of 1894 

 have brought to light some degree of presence of //. schachtii, I give 

 accompanying a Plate with magnified figures of the T. decastatrix, 

 drawn from life by Dr. J. Ritzema Bos ''' (which he is good enough to 

 permit me to make use of). This gives, with the accompanying 

 explanation from same work (see note), all requisite details for micro- 

 scopic identification, and will be of service in showing what are the 

 distinctions between this species of Tylenchus in all its stages, and the 

 two species of Heterodera above-named, which, in their larval and male 

 conditions, bear some resemblance to it. 



Explanation of Plate. 



Fig. 1. Tylenchus devastatrix, female, taken from an Onion-plant ; magnified 

 200 times. 



a, spear ; b, first muscular swelling of the oesophagus ; c, second oesophageal 

 ring; d, e, intestine properly so called; e,f, rectum; /, anal opening; g, excretory 

 pore (orifice of the lateral vessel) ; /(, commencement of the ovary ; i, ovule, with 

 nuclei (or germs), not fertilized; k, first half of the oviduct (tube), with sperma- 

 tozoids ; I, second half of the oviduct, with glands in the wall ; m, anterior portion 

 of the uterus, containing a fertilized egg ; n, sac, with closed extremity, second 

 portion of uterus ; o, vulva. 



Fig. 2. Tylenchus devastatrix, male, taken from an Ouion-plant ; magnified 

 200 times. 



For a, b, c, d, e, and y, see explanation of preceding figure ; /, cloacal opening ; 

 h, commencement of the testis ; /, mother-cells of the spermatozoids (Spermato- 

 blastes) ; k, cells further divided, forming spermatozoids ; /, vas deferens ; m, 

 spicule; li, accessory piece ; o, purse. 



- Fig. 3. Anterior portion of a Tylenchus devastatrix, not fully developed, taken 

 from an Onion-plant ; magnified HO times. 



For a, b, c, and d, see explanation of fig. 1. In front of the spear («) is shown 

 the labial region, and loWer, at the base of the spear, the nniscitli protractorii leading 

 forwards, and the miisculi retractorii leading backwards. The half of the oesophagus 

 in advance of the first bulb, or muscular swelling (6), has a straight direction ; the 



* See Plates I. and II. in 'L'Anguillule de la tige [Tylenchus devastatrix, Kuhn),' 

 ir Dr. J. Ritzema Bos, Prof, a I'lnstitut de I'Etat a Wageniugen. Haarlem, 1888. 



