Agricultural Gazette. 



abundance in the soil, showing that many must have left the tissues in 

 which tiiey were hatched. All tins, however, does not preclude the supposi- 

 tion that some larvas may simply move to a different part of tlie root in 

 wliich they eoininenced their existence and there develop. I merely wish to 

 point out that this is far less probable than that tlicy attack fresh rootlets. 



I have now related what I have learned concerning the life-history of this 

 pest. Much remains to he done, and considering the extent of the devastation 

 caused by allied worms in Europe and the United States, it is to be hoped 

 that the remainder of the investigation will, in duo time, be made. The 

 importance of following the pest througli the seasons of an entire year cannot 

 be too strongly insisted upon. The manner in which this should be done is 

 already indicated, and will now be still further elucidated. The exact time 

 of year, if any exist, in which the larva) issue in greatest numbers from old 

 roots, and begin their migrations to fresh rootlets, should be ascertained. 

 The manner in which the worms are spread from one field to another should 

 be investigated. It is also important to ascertain whether or not the eggs 

 or larva) pass iniinjurcd through the alimentary canal of domestic animals. 

 If they are not injured by that process, manure is likely to become an agent 

 in distributing the pest, for it is perfectly certain that root-crops injured by 

 the worm will be fed to animals. Numerous researches, therefore, remain 

 to be made before the pest can be said to have been properly investigated. 



Systematic. 



Although the foregoing observations are inadequate as a picture of the 

 life history of this worm, they are quite sufficient to indicate its systematic 

 position. Beyond doubt it must be referred to the genus Tylcnchus, a genus 

 already known to contain some of tlie worst enemies of various crops. 

 Ti/hnchus tritici causing a serious disease in wheat, and Ti/lenclms devastatrix, 

 which often sweeps off the onion crop in Europe, may be cited as instances. 

 My reasons for assigning this vi-orm a place in the genus Tylenchus must be 

 given in full, for they affect also the systematic position of a number of 

 worms heretofore reckoned as belonging to a distinct genus, Heterodera. 



The characteristics of the genus Tylenchus may bo briefly given as 

 follows : — Transparent striated round worms, totally devoid of bristles or 

 setfP, varying in length from one-third of a millimetre to three and a half 

 millimetres, attacking the tissues of ])lants, or more rarely animals, by means 

 of a s])car and sucking ap])aratus of the following construction: A three- 

 bulbed spear, capable of being thrust forth and withdrawn by means of 

 appropriate muacles, is connected wdth a powerful median esophageal 

 sucking-bulb by means of a tube whoso lining is more chitinous than is 

 usual in other Nematode genera; the median bulb is connected with a 

 smaller posterior bulb of much weaker construction by means of a shorter 

 and weaker tube, which passes through the oblique nerve-ring, situated just 

 behind the median bulb. The posterior bulb may become quite rudimentary, 

 but probably never quite disap|)ears. Lateral organs as well as visual organs 

 are unknown in the genus. The female sexual ai)paratus is usually single and 

 asymmetrical, being in that case usually straight and directed forward and 

 often presenting a rudimentary posterior branch, but may be double and 

 symmetrical. In the former case the vulva is behind the middle ; in the 

 latter case it is central. The male possesses two etiual, arcuate spicula and 

 a more or less well-developed bursa. Prom this characterization I have 

 puiposely omitted the changes that it will be necessary to make when the 

 present worm and its allies are added to the genus. 



