ON THE ANGUILLULID^. 85 



tlie oesopliagus, constitute also, I believe, in reality, a valvular apparatus, probably con- 

 nected with this same process of suction. 



The power of repairing injuries possessed by these animals seems to be very low. In a 

 specimen of Oiicholaimus vulgaris, the head and oesophageal part of the body were severed 

 from the remaining portion ; and during the three days that the pieces were observed, 

 although both portions continued to move about with tolerable activity, not the slightest 

 attempt at repair w^as seen — no contraction even or closing up of the cut ends, such as 

 almost instantly occurs when a Na'is is similarly injured. The chitinous nature of the 

 integument in the Nematoids almost precludes contraction, and nothing like circular 

 muscles seems to exist. On another occasion I found the anterior half of an individual 

 of the same species moving about freely a fortnight after section of its body, but present- 

 ing no attempt at repair. Similar results have been arrived at with one or two other 

 species, and with sections made in various parts of the body. 



I have not yet obtained much positive information with regard to their duration of 

 existence, but, from what I have seen, suspect it rarely exceeds from six to ten months '. 

 In Ilononchus truncatus I have ascertained that in about two months the embryos had 

 attained two-thirds of thfcir adult size, and were only then beginning to emerge from 

 their asexual condition, the very first rudiments of a genital apparatus being just per- 

 ceptible. The rate of growth after this seems to be still slow and gradual ; and the 

 females appear to die after the production of a single brood or batch of ova. Such is 

 certainly the case with the Vibrio tritici; and, as pointed out by Davaine^, the total 

 duration of the active life of this animal is about nine or ten months. 



The diiferent members of this group vary much as to their tenacity of life. As a rule 

 they are frail and delicate, and do not recover even after a slight desiccation of five 

 or six minutes, thus differing remarkably from what I have at present observed wdth 

 members of the four land and freshwater genera, Tijlelenclius, Flectns, Aplielenclms, 

 and Cephulobus : with all these there is a remarkable tenacity of life and power of 

 recovery after what seems to be complete desiccation. This power of revivification, now so 

 well known to be possessed by the young of the Vibrio tritici, was first ascertained by its 

 discoverer, Turberville Xeedham, in 17d-3 ; and afterwards the same property was recog- 

 nized by Spallanzani in certain species of minute Nematoids found in tufts of moss ; and 

 a series of experiments were instituted by him with the vicAV of estimating the extent 

 of this power. These experiments have been repeated and extended in the most careful 

 and conclusive manner by MM. Davaine^, Doyere'', and Gavarret'' ; and the remarkable 

 advantages proved to be possessed by these minute animals have been erroneously sup- 

 posed by most writers to be characteristic of the whole group*'. I hope to make more 

 extended observations on this head, and to be able to point out more fully hereafter the 

 particular genera in which this capability of resisting desiccation exists, with the ana- 



' The period of those species capable of revivification is, of course, altogether a variable quantity ; and I speak 

 more particularly concerning the active life of the other members of the family. 



^ Recherches sur I'Anguillule du Ble nielle. Paris, 18")". ^ Loc. cit. pp. 39-61. 



* Ann. des Sc. Nat. 2" scr. t. xlv., xvii. & xviii. * Ibid. 4« se'r. t. xi. p. 315. 



' Davaine's observations come very near to the truth in this respect (Ann. des Sc. Nat. scr. 4, 1858, torn. x. p. 335.) 



