Mr. H. J. Carter on Spongiophaga Pottsi. 355 
veloped as the tapeworm in the body of a third animal? The 
nematoid parasites, however, do not appear to be so erratic in 
their course of development or so very different in their meta- 
morphic forms as the Cestoidea ; but they are so numerous in 
species, throughout the animal and vegetable kingdoms, both 
independently and parasitically (that is, externally and inter- 
nally), that there is no saying where they may not present 
themselves, and, in some instances, considerably altered in 
form. ‘Thus the guinea-worm ((laria medinensis), which I 
described and illustrated from specimens in Bombay, some 
years since (‘ Annals,’ 1859, vol. iv. ser. 3, pp. 28 and 98, 
pls. i., ii., and iil.), is always filled with full-grown embryos 
(for no male has yet been found) about 1-33rd inch long, cor- 
rugated transversely and possessing a long, straight, attenu- 
ated tail, while the parent may measure 32 inches, and in 
some instances is stated to reach ‘‘10 to 12 feet,” perfectly 
smooth on the surface, and equally obtuse at each end, with 
an oral aperture, not exceeding 1-600th inch in diameter, in 
the centre of one extremity, and at the other the tail dimi- 
nished to a minute object, curled up and shut in by a membra- 
nous expansion from the body, thus evidencing an amount of 
metamorphosis which, but for the presence of the well-deve- 
loped embryo inside the parent (pl. 1. fig. 6, 1. c.), would be 
incomprehensible. Moreover the extremely minute oral 
orifice and corresponding atrophy of the alimentary canal would 
seem to indicate that its nourishment must have come through 
other sources ; but be that, in part, as it may, the oral orifice is 
not near so small-as that of the cilium of an Acineta (A. 
tuberosa), which, temporarily metamorphosed into a tentacle, 
may in plurality be seen to transfer the contents of Para- 
mecium aurelia (into which they have been projected for this 
purpose) to its own body, by the passage of glairy, fatty, or 
albuminous globules through the centre of the tentacle from the 
Paramecium to the Acineta. Hence the minute size of the 
oral orifice in the guinea-worm may be no indication that it 
receives nourishment in any other way than through the oral 
aperture, although this is so extremely small. 
Slight, however, as the metamorphosis of the guinea-worm 
may appear when compared with that of the Cestoidea (ex. gr. 
the tapeworm), I think that the conjectured one which I am 
about to mention, viz. the metamorphosis of a nematoid worm 
into Spongiophaga, is nearly equal to it. 
As before stated, I have gone into the history &c. of 
Spongiophaga communis (op. et loc. cit.), so have now only to 
refer the reader to it for an introduction to what Iam about 
to state. 
