The adult organisation of Paragordius varius, 441 
This remarkable organ, without nuclei and without cell boundaries 
in its organisation, is difficult to interpret except as an organ ab- 
normally retained in the adult condition but proper to an earlier 
stage. In no other adult, male or female, was any trace of it to be 
found; and in several individuals of this species, as well as of Chor- 
dodes morgani and Gordius aquaticus robustus, the whole intestine 
was dissected out and then stained and mounted, but none of these 
dissections showed such an organ attached to the intestine in any 
portion of its course. This organ is essentially a longitudinal canal 
with lateral branches that open into the body cavity, but with no 
open communication into the intestine to which it is so closely at- 
tached. From these characteristics it might be considered an ex- 
cretory organ, perhaps taking up fluids from the body cavity and by 
osmosis passing them over into the intestine. In any case we may 
conclude that this organ is seldom retained into the adult stage, that 
it properly belongs to an earlier period of the ontogeny, and that 
from its unpaired nature and other structural connections it represents 
a new type of excretory organ. 
This organ as we have seen lies in the medio-ventral body cavity. 
In some adult males, more rarely in females, a staining coagulum is 
found in this cavity, particularly in the anterior portion of its extent 
(M. V. Cav Fig. 90, Pl. 43). This may well represent an excretory 
fluid, and perhaps in the adult condition the medio-ventral cavity re- 
presents an excretory space. In one male was found, however, besides 
this faintly-staining coagulum, a denser staining substance in this 
portion of the body cavity (Fig. 90); and this latter may well re- 
present degenerated substance portions of an excretory organ such as 
that found in the female described. In any case, in the adult or- 
ganisation the only structure that normally represents an excretory 
organ is the medio-ventral body cavity, and since this is not connected 
with any openings in the body wall, the excretory fluids which it 
contains must pass by osmosis into the cavity of the intestine. Yet 
at an earlier stage there is within this cavity, in close contact with 
the dorsal surface of the intestine, an unpaired excretory organ with 
lateral branches; and this organ only rarely persists into the adult 
stage. In an immature female with white cuticula and with the 
muscular epithelium still in process of differentiation, taken from the 
body cavity of an Acheta, no trace of such an organ was found; 
accordingly it must normally be functional at a still earlier stage, 
perhaps in individuals of only a few .centimetres in length. 
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