THE CAUSAL PARASITE. 35 



common center, and the upright legs of the triangle surround a canal 

 through which the spear passes. The hases are united into a small 

 ring just around this canal and another ring unites the outer ends of 

 the basal legs (PI. I, fig. 16). Looked at from the anterior or pos- 

 terior direction this apparatus resembles a wheel with six spokes. 

 Distinct muscle strands run from the rim of this wheel to the knobs 

 of the spear, as well as to the point where it begins to taper. It is 

 probable that this peculiar organ is to help support and guide the 

 spear as the male is battering his way through the tissues. A similar 

 apparatus is present in Ileterodera schachtii, the sugar-beet nematode. 

 It was imperfectly described by Strubell,i but the writer's observa- 

 tion shows it to be essentiall}^ the same as in the root-knot nematode. 

 It has also been reported, but not correctly described, for a Tylenchus 

 species. 



The reproductive organs of the male consist in all cases examined 

 by the wTiter of a single testis, a tube blind at the anterior end and 

 running parallel to the alimentary canal, into which it opens just 

 before the anal opening is reached. Atkinson reports that there are 

 two of these reproductive organs, as is the case with some other 

 nematodes. In all the specimens examined by the writer, however, 

 including specimens from Indiana, South Carolma, and Florida, using 

 the oil immersion lens and viewing the nematodes from different 

 sides, there was not the slightest evidence of a second testis. Cobb ^ 

 also mentions its presence, and as both he and Atkinson are accurate 

 observers it must be that sometimes this occurs. In fact, Atkinson 

 himself later found specimens in which the testis was single.^ Accord- 

 ing to the writer's own observation the right testis is the one that is 

 missing, as the one present is placed somewhat asymmetrically, lying 

 nearly in the left half of the body. 



L}dng on either side of the posterior portion of the alimentary canal 

 and mth their points entering the cloacal chamber are two peculiar, 

 somewhat sickle-shaped bodies, the spicules. These are curved bodies, 

 tapering toward the posterior end, about 35 /i long, measured on the 

 chord connecting the two ends. No accessory piece is present, 

 although a thickening near the apical portion may represent one fused 

 with the spicules. These spicules are of use only during the sexual 

 process. 



The excretory canal is plainly visible in the left lateral line, open- 

 ing ventrally in the median line 160 to 170 /x from the anterior end 

 of the body. 



It seems probable that the mature males take little or no food 

 and that they perish after having performed their function. The 

 reason for this supposition is the fact that one often finds still actively 



I Strubell, 1888. 2 Cobb, 1902. 3 Atkinson, 1889; see also Atkinson, 1896. 



217 



