OF THE NEMATOIDS, PARASITIC AND FEEE. 615 



vacuum with sulphuric acid for four days, and whose contained young even after this 

 process may be revived in less than an hour. The time during which they are allowed 

 to remain active considerably influences their future power of reviviscence ; thus, 

 Davaine finds, " Apres un mois du sejour dans I'eau, la plupart des anguillules desse- 

 chees ont encore la faculte de revenir a la vie. Passe ce temps, elles perdent assez 

 promptement cette faculte. Aussi lorsqu'on met dix jours d'intervalle entre chaque 

 dessication nouvelle, des la quatrieme revivification Ton voit le nombre de celles qui 

 restent mortes augmenter rapidement. La dur^e du temps pendant lequel on garde ces 

 animaux en etat de dessication a peu d'influence sur ce resultat, qui depend en grande 

 partie de la durSe de la vie active." Davaine insists upon the fact that organic matter 

 of any kind undergoing decomposition in the water in which desiccated animals are 

 immersed, will absolutely prevent their exhibiting any movements or signs of life. 

 They remain stifi", straight, and motionless, though not in reality dead ; and from other 

 experiments concerning the noxious properties of even the minutest quantity of am- 

 monia mixed with the fluid containing these animals, he supposes that the deleterious 

 influence of decomposing organic matter may in reality be due to the evolution of minute 

 quantities of ammonia. For interesting details on this subject, and also on the influence 

 of solutions of various poisonous and narcotic alkaloids, I must refer to M. Davaine's 

 interesting memoir. He also dwells upon what I am able to confirm, viz., the fact that 

 the remarkable powers possessed by the young are not shared by the adult Tylenchiis 

 tritici, which does not exhibit any very well-marked tenacity of life. As I shall point 

 out afterwards, however, this is quite exceptional, and is in all probability due to the 

 method of existence of this animal, since in other species of the genus Tylenchus both 

 old and young are similarly endowed in this respect. Elsewhere* M. Davaine having 

 become aware of the fact that all the AnguilluUdae do not possess this same tenacity of 

 life, made a general statement on the subject which comes very near to the tnith ; 

 he thinks that those species Avhich are constantly submerged do not possess this pro 

 perty of recovering even after short periods of desiccation, whilst it is possessed by 

 others, " qui vivent dans les lieux exposes aux alternatives de secheresse et d'humidite." 

 This is a considerable advance upon the popular opinion, Avhich has hitherto regarded 

 all the free Nematoids as endowed with the same remarkable tenacity of life ; although 

 in the right direction, it is, however, too sweeping a generalization. 



The experiments which were conducted in concert by MM. Doyebe and Gavaeret 

 upon the degree of tenacity of life of the Eotiferse and Anguillulidaj found in tufts of 

 moss are of the greatest interest, and the results of their inquiries may be accepted with 

 all the more satisfaction, from the very evident care and caution with which these expe- 

 riments were conducted. Their paper should be studied by all interested in this ques- 

 tion, so startling are its results, and so opposed to all ordinary biological data. I cannot 

 refrain from quoting here the results of one carefully performed scries of experiments, 

 instituted to ascertain the power of resisting simple desiccation at ordinary temperatui'es 



* Ann. des Sc. Nat. A'°' eer. x. 1858, p. 387. 



