The various species of Cosmaria seem to receive substances through the hole (fig. 20. c.), which is constantly open. The Colpopelta has upon the inferior surface, at both extremities of the body, a longitudinal tube (fig. 28. a.), which seems to unite both openings.
In the Closteria we find upon the point of both sides of the cuirass, perforations which I consider as mouths.
In the Closterium Lunula Nitzsch (fig. 56—58.) this mouth (a.) is very easily found; it leads to a very short, and sometimes not well marked tube (b.). Moreover, we observe this orifice in the Closterium caudatum, acuminatum, didymotocum and spirale (fig. 59—67.). In the Closterium costatum each horned extremity of the cuirass is truncated, and a larger, blunt and more opened mouth (fig. 61. 63. b. b.) comes out of its edges. Between this orifice and the content of the animalcule, through which the intestinal tube passes, the Closteria present a peculiar organ, which I name rotatory bladder, without knowing its functions. Some naturalists have taken those bladders for feet; but feet, entirely surrounded with a cuirass, and without any communication with the outside, would answer very ill the purpose of moving.
This spherical organ is always found under the orifice, and in the Closterium Lunula under the mouth (fig. 58. b.) and the intestinal tube. That bladder is transparent, round, circumscribed in itself (fig. 58. c. 62—63, a. 73. e. 65. c.), the number of which
