Introduction to Animal Morphology. 161 



auricular processes on the head ; Rhynchodesmus and Geo- 

 desmus are terrestrial ; Procotyla has a cephalic, and Bdel- 

 lura a caudal sucking disc. 



Order 2. Rhabdocoela. Intestine a simple pouch ; pharynx 

 not protrusible in some ; usually one sex-opening ; testes 

 pouch-like ; many are freshwater, others marine. This 

 order includes five families : i. Microstomidae proctuchous; 

 mouth small, round, terminal in Proporus (eyes none), and 

 Disorus (eyes six), sub-terminal in Vorticerus ; it is slit-like, 

 sub-terminal in Microstomum, terminal in Schizoprora. 

 2. Pharyngeidae pharynx protrusible, somewhat urceolate, 

 cylindrical, or conical ; mouth terminal (Acmostomum), or 

 sub-terminal (Vortex) ; it maybe a transverse (Stenostomum), 

 or a longitudinal slit (Derostomum) ; or central, with a cylin- 

 drical (Mesopharynx), or funnel-shaped pharynx (Chonosto- 

 mum), or post-central, with one (Monocelis), two (Diotis), 

 or no otolith (Opistomum). 3. Apharyngeida,- pharynx 

 not protrusible ; mouth circular, sub-terminal (Strongoylsto- 

 mum), or medio-ventral ; eyes two (Mesostomum), or none 

 (Typhloplana) ; or the mouth may be slit-like, transverse, 

 behind the otolith (Convoluta), or longitudinal, terminal 

 (Telostomum), or sub-terminal ; eyes two (Macrostomum).* 

 4. Rhynchoprobolidae having a terminal proboscis, and a 

 sub-terminal (Prostomum), or central, round mouth (Rhyncho- 

 probolus). 5. Catenulidae several individuals united in a 

 tock by continuous budding; head distinct; 

 European and South African forms. 6. Dinophilidae form 

 a link to the next order, as they have a body cavity in which 

 e proctuchous stomach. They also have a number of 

 girdles of l<mg cilia. 



Order J, Ni mertidea (CErs/ t <!, Rhynchocu-la, Sthu/tzc) 

 j marine, prnrturhous, diu-cious,t 



probe- Turbellarians, with contractile, brittle, 



Midimi-ntal annula- 



tion), and nuiii :nial rniu ij>arous glands, \\ith snmc- 



,i fourth muscular lamina (of internal longitudinal fibres, 



.-glands 11- :aim. 



; ' : I in I'di.i imolutu. 



M 



