<18 DE. II. CHAMLTON BASTIAN ON THE ANATOMY AND PHYSIOLOGY 



individuals, wliich were then removed carefully on the point of a feather and placed on 

 a clean slip of glass. 



After specimens of species belonging to either of the fom* genera Tylenchus, Plectus, 

 Cephalobus, or Aphelenchus had been thus laid on the slip of glass, the time noted, and 

 the animals submitted uncovered to the microscope, I found them lose their form and 

 begin to shrivel only very slowly, and also that after the allotted period of exposure 

 to the desiccating influence of the air was over and some water was added, this seemed 

 to penetrate their bodies very slowly — the gradual process of redistension often occu- 

 pying nearly thirty minutes before the animal was quite restored to its original fonn. 

 The length of time required, however, depends upon and increases with the duration of 

 the period of exposure, and, in almost all cases, after the animal has regained its 

 habitual form it remains for a variable time perfectly still and motionless. In experi- 

 ments* with Plectus parietinKS, I have found that if the period of exposure has been 

 from one to four or five hours, the perfect redistention of the body usually occurs in 

 about twenty-five minutes, and then the slow bending movements which are the firet 

 evidences of returning activity may begin almost immediately afterwards. As a rule, 

 after an exposure of forty-eight, or even thirty-six hours, the animals never recover at 

 all. Exceptions, however, occur : thus, I once saw an animal recover after it had been 

 exposed for five days, though in this case the recovery was proportionally slow, the 

 animal not having completely resumed its natural appearance till four hours after the 

 addition of water, and not having commenced its fii'st slow movements till after the 

 expiration of another two hours. Occasionally the animals do not recover after much 

 shorter periods of exposure than that mentioned above, and sometimes the resumption of 

 activity after the addition of water is much more speedy than usual ; thus, in one instance, 

 an animal which had been exposed and dry for twenty-one houi's, was seen in full activity 

 only eight minutes after the addition of water. So far as I have seen, young specimens 

 are certainly not capable of resisting exposure better than, or even so well as adults. 



When we remember the power these same animals possess of resisting prolonged and 

 complete desiccation in vacuo, as shown by the experiments of MM. Dotkee and 

 Gavarret, it is most striking to find them succumbing in such short periods to the 

 mere desiccating influence of the atmosphere upon their uncovered bodies. How can 

 we explain this without imagining the direct contact of atmospheric air to have a delete- 

 rious influence upon their tissues'? 



With animals belonging to the genera Chromadora, Enoplus, Monhystera, Leptosoma- 

 tum, 3Iononchus, Porylaimus, and many others, the results have been almost uniform. 

 I have never succeeded in restoring any of these animals after they have remained dry 

 and motionless on glass for two minutes ; many would not recover after one minute of 

 such exposure, and with Chromadora communis I have rarely been able to revive speci- 

 mens after even half a minute's exposure, dating from the time of the cessation of move- 

 ment in the drying animal as seen under the microscope. All these animals shrivel 



* Temperature of room (summer) 70^° F. 



