410 ON A BECENTLY DISCOVERED TURBELLARIAN WORM. [Mar. 1, 



indication of its habit — this being the first recorded parasitic Acoel 

 (hi.) — I suggested incola as the specific name. 



Note on the ProporidjE. 



V. Grafi* in his recent monograph (i.) divided the Proporidse — 

 Acoela with one genital pore — into two genera : (a) Proporus, 

 (b) Monoporihs. In both these the male and female ducts open 

 into a common atrium genitale which communicates with the 

 exterior by a single aperture. They are distinguished from each 

 other by the absence and presence respectively of a spermotheca. 



Since then (1890) some further contributions have been made 

 to our knowledge of this family. In 1892 v. Grafi" (ii.) drew 

 attention to the turbellarian characters of Haplodiscus piger 

 (Weldon). In 1895 Bohmig (iv.) described six new species of 

 this genus and corroborated Weldon's observation of the absence 

 of female accessoria. The following year Sabussow (v.) recorded 

 another species, on which also Monticelli wrote (vi.). In 1899 

 Sabussow (v.) obtained from the White Sea an Accel to which he 

 gave the name Bohmigia iniaris-alhi (vii.). 



Bcihmig's classification of the family is as follows : — 



" Genera — (a) Monoporus — Proporidpe mit Bursa-seminalis, &c. 



(b) Proporus — Proporidje ohne Bursa-seminalis, &c. 



(c) Haplodiscus — Proporida? ohne Bui-sa-seminalis. 



Die Mundoffnung findet sich in oder hinter der 



mitte der Bauchflache. Der Phaiynx ist, wenn 



vorhanden, kurz und wenig entwickelt. Der 



Korperform ist platt scheibenformig." 



He thus distinguishes Proporus and Haplodiscus merely by the 



position of the mouth, the size of pharynx, and shape of body, 



while he ignores the absence in Hap>lodiscu,s of the "atrium 



genitale " in the other two genera. 



Now it has been shown above (p. 409) that in Avagina the 

 female apparatus is incomplete, the ova being extruded through a 

 temporary opening which has no connection with that of the male 

 organ. As in Haplodiscus there is a similar absence of vagina, it 

 seems not improbable that a like method of ova-extrusion also 

 obtains. 



The union of the male and female systems to form a common 

 genital atrium in the genera Proporus, Monoporus and Bohmigia, 

 and their total separation in Haplodiscus and Avagina, seem to 

 render desirable a svibdivision of the family as under : — 



Family Proporid^ : Accela with one genital aperture. 



Subfamilies I. Proporince : to include those Proporidse 

 with a common genital atrium. 



Genera : (a) Proporus, (b) Monoporiis, 

 (c) Bohmigia. 

 II. Avaginiolce : to comprise those Proporidse 

 with male accessoria only. 



Genera : {&),Haplodiscits, (b) Avagina. 



