ROTATORIA OF THE UNITED STATES. 
307 
Internal organs . — The eye lies at the posterior end of the brain and appears in dorsal view to 
the left of the ridge (fig. 1, e.). The two mucus reservoirs are of equal size, and each opens sepa- 
rately at the base of one of the toes. The trophi are well developed, and in this species their 
asymmetry reaches perhaps its highest development. The left manubrium is long and heavy; the 
right one a mere rudiment — a short, slender spicule (fig. 2). The other internal organs call for no 
special remark. 
Measurements. — Length of body, 0.175 to 0.225 mm.; of toes, 0.050 to 0.075 mm.; total, 0.225 to 
0.300 mm. 
Movements . — For an account of the movements of this species, see the general discussion of the 
movements of the Rattulidce, p. 295. 
History. — In the systematic and faunistic literature this species has long been confused in a 
very curious way with another to which it bears very little resemblance, namely, with Diurella 
porcellus G-osse ( D . tigris Bory). This is due to the fact that both received the name tigris, one 
from Muller, the other from Bory de St. Vincent, and they have often since been supposed to be 
identical. Ehrenberg (1838) confused the two, citing Bory's D. tigris as a synonym of his 
Notommata, tigris. Gosse, in Hudson & Gosse's Monograph (1889), describes the present animal 
as Rattulus tigris, but notes in a rather perplexed way that Eckstein’s account (1883) of the animal 
does not agree with his own. Eckstein had described under this name Bory’s. species ( Diurella 
porcellus Gosse). Bilfinger (1894, p. 51) seems to have been the first to set forth clearly the fact 
that Elirenberg’s Notommata, tigris and Bory’s Diurella tigris are two distinct animals. Attention 
has been called to the same fact by Weber (1898, p. 513) and probably by others. It will be well 
to give here a list of the animals mentioned by different authors under the specific name tigris 
(assigned to various genera), specifying in each case which of the two animals, Diurella tigris 
Muller or D. porcellus Gosse, was really meant, so far as that can be determined. 
Trichoda tigris Muller (1786)= Diurella tigris Mliller. 
Diurella tigris Bory de St. Vincent (1824) = D. porcellus Gosse. 
Notommata tigris , Ehrenberg (1838, 1838) =D. tigris Muller. 
Notommata tigris , Perty (1852) =D. tigris Muller. 
Notommata tigris, Pritchard (1861) =D. tigris Muller. 
Monommata tigris, Bartsch (1870, 1877) =D. tigris Muller. 
Diurella tigris, Eckstein (1883)=Z>. porcellus Gosse. 
D. tigris, Herrick (1885) = D. porcellus Gosse. 
D. tigris, Eyferth (1885). — The figure seems to represent D. tigris Muller, but the description applies best to D. por- 
cellus Gosse. 
D. tigris, Plate (1886) =Z). porcellus Gosse. 
I), tigris, Bloclimann (1886)=D. porcellus Gosse. 
Acanthoclactylus tigris, Tessin (1886) =D. porcellus Gosse. 
Rattulus tigris , Hudson & Gosse (1889) —D. tigris Muller, a 
Rattulus tigris, Wierzejski (1893 )=D. porcellus Gosse (?). 
Rattulus tigris, Levander (1894 )—D. porcellus Gosse. 
Rattulus tigris , Hood (1895) =D. tigris Muller. 
Rattulus tigris, Scorikow (1896). — The description does not agree with either of the species under consideration. 
Rattulus tigris, Stenroos (1898) = D. tigris Mliller. 
Rattulus tigris, Jennings (1900, 1901) =D. tigris Muller. 
Distribution. — In America Diurella tigris Muller is very common in aquatic vegetation in the 
quiet parts of streams and lakes. I have recorded its presence in the following localities: Put-in 
Bay Harbor and East Harbor, Lake Erie; Huron River at Ann Arbor. Mich.; Portage River, Ohio. 
It has also been recorded from Bangor, Me., by “ J. C. S.” (1883) , and from the neighborhood of 
Cincinnati, Ohio, by Turner (1892), but it is impossible to say in these cases which of the two 
species that have gone under this name ( D . tigris Muller or I), porcellus Gosse) was meant. 
In' Europe: England (Gosse, 1889); Ireland (Glasscott, 1893; Hood, 1895); Germany, near 
Tubingen (Bartsch, 1870) , and in Wurttemberg (Bilfinger, 1894) ; Tyrol (Dalla Torre, 1889) ; Hun- 
gary (Bartsch, 1877; Kertesz, 1894); Lake Nurmijarvi, in Finland (Stenroos, 1898). 
Also in India, near Calcutta (Anderson, 1889); New Guinea (Daday, 1901); Ceylon (Daday, 
1898); Natal, South Africa (Kirkman, 1901). 
a In a previous paper, (Jennings 1900) I was inclined to believe that the animal described and figured by Gosse 
was not the real Notommata tigris of Ehrenberg, owing to the disproportionately large size of the anterior end in 
Gosse’s figure, as well as to the unusual form of the body. But after studying many specimens of this and other 
Rattulidce I am convinced that Gosse’s figure is a poorly drawn representation of a much contracted specimen of 
this species. 
