88 



Journal of Agriculture. 



[lo Feb., 1910. 



has become tougher and not so easil\ ruptured. \w the still older cvsts 

 these germinal cells become aggregated into oval clumps within the tube, 

 acquire an en\-elope, and later on become perfect eggs. 



In the older potatoes the cyst is easily removed for the purpose of ob- 

 servation, the wall of the cyst which is really the epidermis of the dead 

 worm becoming tougher as the potato dries. If a piece of dried potato 

 containing the cystic form of the worm be placed in water, the wall swells 

 slightly, becomes softer, and is more easily ruptured. On placing individual 

 cysts in water they swell up b\- osmosis, a portion of the contents usuallv 

 being expressed. From the contained eggs living worms are hatched out 

 in eight davs ; this, nn dnubt, is much slower than it will be in natural 



SECTION OF POTATO SHOWIXG NEMATODE CVSTS 



conditions owing to the difficulty of keeping the eggs with just the requisite 

 amount of moisture. Some cysts show no development of eggs, only con- 

 taining the germinal cells before spoken of ; these may be non-impregnated 

 females, but more probably the non- development is due to the artificial 

 conditions under which the observations were necessarily conducted. 



The Egg. 

 The envelojje of the egg is chitinous and is very resistant to chemicals, 

 drying, or moisture. It is provided with a process which enables the 

 embrvo to escape, one end coming off like a little lid or cap. The move- 

 ment of the embryo within the egg is very slow, observations having f.re- 

 (juently to be conducted for hours before any movement can be detected. 

 This differs markedly from the embryo of the onion worm which is very 

 active inside the egg and ruptures the envelope by its own activity. The 

 eggs differ greatly in their rate of development, karyokinesis going on more 

 rapidlv in some than in others ; this to a great extent is probably due to the 

 artificial conditions under which the observations are carried out. In many 

 of the Xematoda, division of the embryo occurs very rapidly. If eggs 

 are dried for weeks and then moistened, the embryos show movements in tlie 

 egg within 48 hours. 



