Extract During the last several years the pathogenicity of the immature stages of bursate nematodes has become more and more appreciated, as has the important part played by the immature histotropic stages in retarded infestations. The techniques described by Herlich (1956) Ciordia, H. , Vegors, H. H. and Bizzell, W. E. 1957. J. Parasit., 43: 532–532. [Google Scholar] and Ciordia et al. (1957) Herlich, H. 1956. Proc. Helminth. Soc. Wash., 23: 102–102. [Google Scholar] have, therefore, become of considerable value.