THE ECONOMIC VALUE OF A STUDY OF THE 

 NEMATODES, WITH REMAEKS ON THE LIFE 

 HISTOEY OF HETERODERA IN SOUTH AFEICA. 



By J. Sandground, M.Sc, 



Lecturer in TjOology, University College, Johannesburg. 



Read July 15, 1920. 



The numerous difficulties associated with the study of tlie 

 Nematodes, or " thread-worms," has not tended to encourage 

 investigation on this important group, with the result that at 

 the present time probably rather less is known about the grouj) 

 than (^' any other of comparable magnitude. Many problems 

 of the biology even of some of the better known members of 

 the group remain unsettled, while the existing knowledge 

 of the affiuities of the group as a whole with other groups of 

 the animal kingdom leaves much to be desired. Numerically, 

 the Nematodes are a very large group, and the variety of form 

 that they;, exhibit is said to rival that of the insects. 

 Correlated with this great variety in form is found an equally 

 large variety in habits, ranging from the free-living 

 Anguillulidae, and j) regressing by almost imperceptible 

 gradations until the completely parasitic existence, such as is 

 found in many of the members of the Filariidae and Trichi- 

 nellidae, is assumed. Some of the members of the group 

 possess a remarkable plasticity in habit, and are able to adapt 

 themselves to most profound change in habitat and other 

 surrounding influences, demonstrating the phenomenon of 

 incipient parasitism clearly. As an example, Anguilluln 

 putrefaciens, normally found in decaying onions, is recorded 

 from the stomach of a man suffering from nausea. Again, 

 Rhahditis peUio, a free-living inhabitant of damp soil, has 

 been described as causing vaginal infections, and has further- 

 more been found capable of infecting rats when experimentally 

 introduced. 



Dr. N. A. Cobb, an eminent authority on free-living and 

 plant-parasitising Nematodes, in reviewing the vastness of 

 the numbers of the Nematodes, the enormous variety of their 

 forms and the important relationships that they bear to man- 

 kind, states: " The Nematodes offer an exceptional field of 

 study, and probably constitute almost the last great organic 

 group worthy of a separate branch of biological science com- 

 I'arable with Entomology." For this new branch of science 

 the name " Nematology " is proposed by Cobb, althougli the 

 term " Helminthology " is well established and includes the 

 studv of these forms. 



