102 JOURNAL OF THE 



He is also inclined to think that the gronnds for considering the 

 two species distinct are questionable. In a foot-note, p. 11, 

 he states that he is strengthened in his belief by the recent 

 researches of Ritzema Bos in Wageningen (Biolog. Central l)latt, 

 Bd. VII), who finds that such species as Tylenchus devastatrixy 

 allii, Havensteimi et Askenasyi must be united into a single spe- 

 cies. 



That these two species of Heterodera are identical has been 

 suggested by others.* 



Durino^ mv study of Heterodera radicicola I have been stron^rlv 

 inclined to consider it identical with Heterodera Schachtii since 

 many of the variations of the two species tend to reconcile the 

 above-mentioned differences. However, since my copy of Stru- 

 belPs work has arrived and I have had an opportunity to com- 

 pare it carefully with my own researches I find there exists a 

 difference in the structure of the males of very great morpho- 

 logical importance. Strubell states that the genital apparatus of 

 the male is an un[)aired tube,t the single tube occupies the ven- 

 tral side of the body cavity for half its length, the posterior end 

 unites with a short efferent duct which itself unites with the 

 intestine to form the cloaca. As I have stated in a former para- 

 graph the genital apparatus in the males I have studied is paired, 

 the two tubes unite near the posterior end of the body to form 

 the efferent duct. It is difficult to see how Strubell could have 

 overlooked a second tube, if it existed, since his work was done 

 under the cTgis of Leuckart. This character possessed by com- 

 paratively a few neniatodes seems of too great importance for 

 specific variation. To re-assure myself I referred again to my 

 microscopic mounts of the male. Midler's [loc. cit.) imperfect 

 study of the male leaves us no clue as to the structure of the 

 genital apparatus in Heterodera radicicola. Until the European 

 species is studied it will be impossible to say whether mine is a 

 distinct species. 



*Sorauer, Pflanzcnkrankheiten, Zweite Aiiflage, Erster Band. Foot-note, pp. 854,855, 



t"Bei unseren Heterodera prasentiert sich derselbe als ein einfaclier Schlanch," etc., 

 p. 22. See also his Fig. 1, Taf. I. 



