ON THE ANGUILLULIDÆ. 85 
the cesophagus, 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. Ina 
specimen of Oncholaimus vulgaris, the head and cesophageal 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 was seen—no contraction even or closing up of the cut ends, such as 
almost instantly occurs when a Nats 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 Mononchus truncatus I have ascertained that in about two months the embryos had 
attained two-thirds of their 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 different 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 with 
members of the four land and freshwater genera, Tylelenchus, Plectus, Aphelenchus, 
and Cephalobus: 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 Needham, in 1743; 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 view 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 
ig particularly concerning the active life of the other members of the family. | 
; Recherches sur l'Anguillule du Blé niellé. Paris, 1857. * Loc. cit. pP. nun 
Ann. des Sc. Nat. 2* ser. t. xiv., xvii. & xviii. * Ibid. 4° ser. t. xi. p. 315. 
* Davaine’s observations come very near to the truth in this respect (Ann. des Se. Nat. ser. 4, 1858, tom. x. p. 335.) 
