274 Black Currant Eehoorm 



Excretory system. I have not been able to see anything of this. 



To what species or genus are we to ascribe this black currant nema- 

 tode? 



Some years ago correspondence was undertaken with Professor 

 J. Kitzema Bos and Dr G. de Man to both of whom, as specialists in 

 this group of nematodes, specimens of the species described above were 

 sent. They kindly examined the specimens but neither was able to say 

 definitely whether the species was a form undescribed hitherto or not, 

 but both agreed that it should be placed in the genus Aphelenchus. 

 The chief difficulty which presented itself to Dr G. de Man was the 

 insufficient description of the species already described. Although 

 much remains still to be determined, I have been able to clear up 

 a good many points in my description given above which I hope may 

 be useful to other workers in this field. 



The species with which Dr G. de Man was inclined to identify this 

 black currant nematode is A. fragariae; but quite apart from what 

 seem to be anatomical differences the facts given on p. 264, with regard 

 to the life history and habits of the two forms, make the identity 

 extremely improbable. 



I would suggest that the species does not belong to the genus 

 Aphelenchus at all. 



Professor Bos says of the reproduction organ of the female A. fra- 

 gariae "that the ovary is double, one lies in front of the genital opening 

 the other behind." It is possible that the condition is really as 

 described above for the black currant species, and that the hindwardly 

 directed tube is not an ovary, but a receptaculum seminis. 



Ritzema Bos also describes A. orwerodis, a smaller species than 

 A. fragariae, also found on the strawberry plant and causing disease. 

 In one particular this species may be more like the black currant 

 species. This is the spicule. It is drawn as a slightly curved spicule 

 with a much smaller accessory piece quite unattached to it in front. 

 "The spicules are rather large, more developed than in A. fragariae: 

 also I found here an accessory piece." It is possible that this 

 description is not accurate, but it is something like the idea which 

 one receives from a cursory glance at the spicules ot the black currant 

 species. If it is accurate, then clearly the two species differ con- 

 siderably. Here again experiment failed to establish the black currant 

 species upon the strawberry plant. 



To sum up: 



The reasons against the identity of this species with A. fragariae are 



