Mr. H. J. Carter on Spongiophaga Pottsi. 361 
result ; so I must leave the subject as it is, hoping that Mr. 
Potts, by obtaining the freshwater species and examining it 
alive in its natural element, may be able to clear up the 
mystery that attends the life-history of both, which it seems 
hardly possible to do with the marine species alone, on 
account of the rapidity with which the salt water becomes 
putrescent. 
As regards the interunion without appreciable line of de- 
marcation between the fixed end of the filament in Spongio- 
phaga Pottsi and the additional “ prolongation” and thickening | 
of the chitinous coat of the statoblast (fig. 2, f), the latter may 
be likened to that which takes place in the formation of the 
gall in the oak tree when the insect deposits its egg on the 
bark, to which I have before alluded * ; while the former is 
of every-day occurrence in the polyp which imbeds itself in 
the dermal sarcode of a sponge; and the metamorphosis of 
the complicated elements of a parasitic crustacean into a single 
trumpet-shaped sucking-tube is hardly less than would be 
that of the oral extremity of a nematoid worm into the form 
of the fixed end of the filament of Spongiophaga Pottst. ‘This, 
however, must not be regarded as “ special pleading ;” for as 
yet I do not see either in the marine or freshwater species, or 
in both together, enough to point out what the parasite is, 
further than that I must now renounce the opinion altogether 
of its belonging to the vegetable kingdom, as J can also now 
assert that it is to be found in the freshwater as well as in the 
marine sponges, growing in some specimens, and noé in others, 
of the same species of the Spongida. 
EXPLANATION OF PLATE XVII. 
Fig. 1. Statoblast of undescribed species of Spongilla (gen. 2, Meyenia, 
Carter) from Philadelphia, bearing three filaments of Spongio- 
phaga Potts. Scale 1-48th to 1-1800th inch. a, germinal 
contents of statoblast ; 6, delicate membranous envelope of the 
same; c, chitinous coat (indicated by the dark line); d, spicu- 
liferous layer (the dotted line outside); e, process of chitinous 
coat, opening into 7, tubular prolongation from the same; ggg, 
filaments of Spongiophaga Potts:. ‘The latter are diagrammatic 
in point of length, which is much longer than that delineated. 
Fig. 2. Process of chitinous coat &c. of the same, bearing two filaments 
of Spongiophaga Potts: truncated. Scale 1-24th to 1-6000th inch, 
thus much more magnified to facilitate explanation, as follows:— 
* In Spongilla friabilis, Leidy, 1851,=S. Lordu, Bk., 1863, the prolon- 
gation, however, is natural, and, as pointed out by Mr. Potts, bent sharply 
to one side like the iron ventilators of a steam-vessel; but it appears to 
me to be produced by an elongation of the process of the chitinous coat 
itself, and not by an additional portion like that accompanying the pre- 
sence of Spongiophaga Pottst (Pl. XVII. fig. 1, f, &c.). 
