NATURE OF THE DRACUNCULUS, OR GUINEAWORM. 127 
but no trace of it has yet been found in Copepoda, Cirripedia, Peecilopoda, Edriophthalmia, 
or Podophthalmia. In the Myriapoda and Arachnida the process is not known; but we 
find it inthe highest Articulata—the Insecta—and this not, so far as we know at present, 
in Aptera or Orthoptera, but in a few Hemiptera, Hymenoptera, and Lepidoptera; and 
there is every reason to believe that it only occurs in isolated, though perhaps in many, 
genera of these orders. Take the Mollusca again: agamogenesis occurs in the Polyzoa 
and Ascidioida, not in the Brachiopoda. It is not known to occur in any of the Lamel- 
libranchiata ; and among the higher Mollusca, the nearest approach to it is presented by 
the animal (whatever it is) which gives rise to the ‘Synapta-Schnecken’ (high Gastero- 
pods) and by the Hectocotyligenous Cephalopoda.” 
The fact that neither vulva nor vagina is discoverable in the Guineaworm would, if 
their absence were absolutely proved, throw us back upon this process of agamogenesis, 
in whieh the young are produced from pseudova without the influence of a male, as the 
only possible explanation. Such a defective development of the female generative organs 
in Dracunculus, as compared with their observed condition in the microscopie Filaride, 
ean be met also by a similar suppression of parts, though to a minor extent, in the vivi- 
parous females of the Aphis, in which the spermatheca and two colleterial glands have been 
shown to be wanting, though found in connexion with the vagina of the oviparous female*. 
In support of this opinion also we have the probability that, throughout the whole 
parasitic stage of the life of this Entozoon, germs are being actively produced in every 
part of the genital tube, seeing that in six specimens of the worm, taken from the human 
body after a residence in it of eight or nine months, this formative process was actually 
going on up to the very time of their extraction—as proved by the uniform dissemination 
of erowds of pseudova and young, in the very earliest stages of development. How, unless 
we resort to the phenomena of agamogenesis, can we account for this amazing fecundity 
at a time so remote from the only period when union with a male was possible? For 
even were the worm possessed of the most capacious spermatheca, it must long since have 
been obliterated by the distention of the genital tube, considering that this has become 
closely adherent to the parietes of the body ; yet, nevertheless, up to the very last does 
this wholesale production and development of germs continue. What, then, are we to 
consider as the stimuli so efficacious in the production of pseudova and young in the virgin 
Guineaworm? Doubtless the two very conditions which have been proved to be so neces- 
sary for the continuance of agamic reproduction in the Aphis, concerning which Professor 
Huxley remarks, “The number of successive broods has no certain limit,” till “on the 
setting in of cold weather, or in some cases on the failure of nourishment, the weather 
being still warm, males and oviparous females are produced.” But, located as it is in the 
body of a warm-blooded animal, the Guineaworm is subjected in the highest degree to the 
influence of these two very conditions—being constantly maintained at a high and uniform 
temperature, and supplied by imbibition with nutritive and highly organized fluids. 
* Is there any possible connexion between the special direction of the arrested development which has led to the 
non-formation of the outlets of the genital organs only in the Guineaworm, and the fact before stated, that the young 
or ova of Nematoid worms are frequently discharged by a simultaneous rupture of theinteguments and some portion of 
the containing tube? " 
S 
