TURBELLARIA 



159 



no vasa dcferentia or oviducts being present. The subclass contains 2 

 families and about 40 species, of which 6 have been found in America. 

 Key to the families of Acoela: 



0,1 One genital pore present ................................. 1. PBOPOBIDAE 



o 2 Two genital pores present .............................. 2. CONVOLUTIDAE 



FAMILY 1. PEOPOEIDAE. 



But one genital pore present; position of mouth various: 5 genera 

 and 14 species. 



1. CHILDIA von Graff. Mouth in ventral surface behind the middle; 

 pharynx absent ; bursa semi- 



nalis absent; 2 male copu- 

 latory organs, each with a 

 chitinous stilet : 1 species. 



C. spinosa v. Gr. (Fig. 

 253). Length 1.4 mm.; 

 color light yellow: Woods 

 Hole. 



2. ANAPERTTS von Gr. 

 Body elongate; bursa sem- 

 inalis and pharynx absent: 

 1 species. 



A. gardineri v. Gr. 

 (Fig. 254). Length up to 

 6 mm. ; width 1 mm. ; color 

 red, but yellow at the two 

 ends: Woods Hole, with 

 Potychcerus caudatus, which 

 it resembles, but is much 

 less numerous than it; 

 movements rapid. 



Fig. 254 



Fig. 253 Childia spinosa (von Graff). 1, stato- 

 cyst ; 2, ovary ; 3, mouth ; 4, penis ; 5, genital pore. 

 Fig. 254 Anaperus gardineri (von Graff). 1, stato- 

 cyst ; 2, mouth ; 3, ovary ; 4, genital pore. 



FAMILY 2. CONVOLUTIDAE. 



Two genital pores present, the female pore being in front of the 

 male; bursa seminalis present; mouth near the middle of the body: 5 

 genera and 25 species. 



1. APHANOSTOMA CErsted. Body cylindrical or flattened beneath 

 and narrowed behind; mouth near the middle; statocyst present; eyes 

 absent: 2 species. 



A. diversicolor CErst. (Fig. 255). Body very variable in shape, 

 elliptical, with yellow at forward end; middle usually violet; length 

 1 mm. ; width .25 mm. : Newport, R. I., and Woods Hole, among algae in 

 shallow water, common; Europe, 



