268 Black Currant Eelworm 



In many biological details however the worm is comparable to 

 Tylenchus angustus which nematode causes a disease of rice known as 

 "Ufra" in India. On this host the entirely ectoparasitic habits of 

 the worms which are so marked a feature in the life history of the 

 black currant worm have also been established. Another point of 

 interest is the failure of the rice worm to reach the growing point of 

 the plant, which again results from the tightness of the final enveloping 

 leaves of the bud. 



In the biological work on the black currant eelworm an endeavour 

 has been made to throw light on those periods which are of vital im- 

 portance to the life of the organism and the relation of that organism 

 to the natural conditions which surround it. 



The morphology of the worm however presented difficulties which 

 rendered comparison with closely allied species almost impossible. 

 For these, hasty descriptions and inadequate drawings of the species 

 previously described added to real difficulties in the matter of staining 

 of the worm under consideration were responsible. 



It was therefore with much gratitude that I accepted the help of 

 Dr Assheton to whom I am indebted for the following description 

 and some of the drawings which accompany it. 



It is hoped that such biological and morphological work will at 

 least form a basis for comparison or that it will prove of use should the 

 worm appear on hosts other than that on which its parasitism has 

 been established. 



Morphological details. 



The difficulty of determining the details of the internal anatomy 

 with accuracy is great owing to the thickness of the chitinous cuticle 

 which covers it and prevents the penetration of staining fluids. A 

 combination of platinic chloride, acetic acid and osmic acid (Hermann's 

 fluid) fixes and stains slightly the internal tissues and renders them 

 more easily observable. If the worm is bisected on this fixation 

 with Hermann's fluid and then left for 24 hours in Ranvier's Picro- 

 carmine very fairly well stained pieces can be obtained. 



External character. This nematode measures rather less than one 

 millimetre in length— the largest specimen measured, which was a 

 female, was -92 mm. in length. The males as a rule are slightly 

 smaller. In width the female is always slightly broader than the male, 

 and when containing a fully formed egg it is markedly so, but it does 

 not exceed -04 mm. at its broadest point which is near to the middle 



