112 DISEASES OF FIELD & GARDEX CROPS. [CH. 



have died, and the eggs have burst and produced 

 young. 



In voL xxv. of the Transactions of the Linnean Society 

 Dr. H. C. Bastian has described several other species of 

 Nematode found on and in wheat, oats, and other grasses. 

 Dr. Bastian specially adverts to the tenacity of life belong- 

 ing to the species found under the genus Tylenchus, and 

 he attributes this vital tenacity in part to the structure 

 of the integument of the animals. This integument is of 

 such a nature that it enables the Nematodes to resist 





FIG. 46. 



Fragment of the wall of an Ear-Cockle gall, with part of a colony of 



Nematoid worms, Tylenchus tritici, Bast. 



Enlarged 40 diameters. 



dessication, and prevents the evaporation of moisture 

 through their tissues. Whilst some Nematodes immedi- 

 ately shrivel up when immersed in gelatine, Dr. Bastian 

 has found that members of the genus Tylenchus will move 

 about in gelatine from fifteen to twenty minutes. The 

 power of remaining in a dormant deathlike state for a 

 long series of years Dr. Bastian attributes to some in- 

 herent peculiarities of the animals' tissues beyond the 

 reach of detection by optical instruments of even the 

 highest power. The same author say it is an estab- 

 lished fact that Tylenchus tritici, Bast., is capable of 



