1903.] NATURAL SCIENCES OF PHILADELPHIA. 383 



prey. Generally they are held stiff and rigid; but at times wave-hke 

 undulations are seen to pass slowly along them. Unhke a heUozoan 

 pseudopodiuni there is no supporting axial filament within them. 

 Ambigua has cilia like those of campanulata, and also fringing the 

 whole coronal margin. In these two species and in coronetta the ciha 

 project out of the anterior end of the bodj^ in a thick tuft when the 

 animal is strongly contracted. 



In the foot the hypodermis is thicker than in the trunk, composed 

 of larger cells. Its cells are largest at the junction of the trunk with 

 the foot (PI. XIX, fig. 20; PI. XX, 22, 23, 25, 27, 28); and these may 

 be gland cells which produce the gelatinous tube. The peduncle (figs. 

 24, 40) is homogeneous without cells or nuclei ; it probably represents 

 a secretion of certain large hypodermal cells found in the embryo but 

 absent in the adult, which are placed at the distal end of the foot (PL 

 XXI, fig. 38). The peduncle is firmly attached to the plant stem, so 

 securely that when the animal is torn loose from its tube the peduncle 

 is often left still attached. 



Alimentary tract. — The following regions are marked in all the forms : 

 infundibulum, vestibulum, oesophageal tube, proventriculus, stomach, 

 posterior intestine, rectum, cloaca. 



The infundibulum {Inf., figs. 20, 22, 25, 28) is the cavity of the ante- 

 rior portion of the corona, and its opening to the exterior constitutes 

 the broad mouth. It is lined by a thin one-laj^ered epithelium in which 

 nuclei can be distinguished by staining, is without cilia, and its wall 

 is separated from the hypodermis to which it is attached only at its 

 anterior margins, by the body cavity. The infundil)uhun is partially 

 bounded off from the vestibulum behind it by the diaphragm. This 

 {Dia., figs. 22, 23, 25, 27, 28) is a thickened annular fold of the internal 

 wall of the alimentary tract, and the only portion of the latter anterior 

 to the stomach which is ciliated. Viewed from in front, i.e., from the 

 mouth opening, it appears circular with a knob-like thickening at each 

 side in campanulata (fig. 31). Each of these knobs bears a tuft of long 

 and slowly vibratile cilia, while the border of the diaphragm ventral to 

 these knobs bears a semicircle of very short and delicate, rapidly 

 vibratile cilia. There are no cilia dorsal to the knobs. In conklini 

 (fig. 25) the relations are in general similar. In coronetta (figs. 22, 23) 

 the dorsal free margin of the diaphragm is considerably thicker, and 

 bears short pointed projections (like those within the infundibulum 

 of Apsilus) ; while the ventral margin bears rather long cilia upon sev- 

 eral knobs. In all these species (I did not determine the relations in 

 ambigua) the cilia appear usually to beat forward, i.e., into the in- 



