1903.] NATURAL SCIENCES OF PHILADELPHIA. 365 



name Didyophora is preoccupied, and proposed to recognize" as three 

 distinct species Apsilus vorax (Leidy), A. bipera Foiilke and A. biicine- 

 dax (Forbes). In rejoinder to this paper Leidy, in the same 3^ear, pro- 

 posed to unite these under the name Apsilus vorax, and found at last 

 the lateral antennae. Hudson and Gosse (1886) placed vorax and hucin- 

 edax as synonyms of lentiformis, and hipera as a distinct species ; they 

 relegated this genus to the FlosculariidcB. Stokes (1896) gave a good 

 description of bucinedax, from Trenton, N. J.; he described the lateral 

 antennae, oesophageal tube, long immobile setae arranged in tufts upon 

 elevations of the inner surface of the coronal cup, slender and numerous 

 coronal muscles, an ovary extending across the whole width of the 

 body. He also figures the corona of bipera from the same locahty, and 

 considers the four described species as all distinct. Lund (1899) held 

 that the genus should be removed from the Flosculariidce, and placed 

 in a separate family near the Asplanchnidce. Jennings (1900) figured 

 the young of a species of Apsilus. Finally Gast (1900) has given a very 

 detailed and accurate account of the anatomy and histology of a species 

 he calls vorax Leidy (holding lentiformis to be synonymous), and 

 regards bipera and bucinedax to be distinct from it. 



Thus the European species, lentiformis, has been well described by 

 Mecznikow and Gast, but of the three described American species the 

 accounts, with the exception of that of Stokes of bucinedax, are so 

 meager that the status of these is very perplexing. Foulke was right 

 in uniting all these in the one genus Apsilus. A. bucinedax (Forbes) 

 is well marked from all the others by the shape and great size of its 

 germariurii. Now the species which I shall describe is from the same 

 locality as the forms described by Leidy and Foulke, and agrees with 

 both of these in all essential particulars (these authors had overlooked 

 the germaria, nephridia and foot, all the sense-organs except the 

 lateral antennae, and the oesophageal tube). Foulke considered her 

 species to differ from Leidy's in possessing lateral antennae (but these 

 had been overlooked by Leidy), in cihation of the corona (probably, as 

 Gast has remarked, flame cells were mistaken for such ciliation), in 

 more strongly developed muscular system, and in the external form. 

 I am inclined to conclude that these differences are only apparent, due 

 to the meagerness of Leidy's descriptions. Stokes stated that bipera 

 differed from vorax in that the ventral margin of the corona is projected 

 forward; but in the form described by me this margin shows consid- 

 erable variations in form. Hence bipera (Foulke) had best be consid- 

 ered a synonym of vorax (Leidy); and the three clearly recognizable 

 species may be distinguished as follows: 



