BRITISH MARINE TURBELLARIA. 221 



Subfamily Allostomin;k. 



Plagiostomidce toith one ventral and posterior genital aperture. Two 



germana and two distinct vitellaria. Pharynx placed in the hinder 



half of the body, its mouth directed posteriorly. 



This subfamily, as constituted by v. Graff, includes the genera 



Enterostoma and Allostoma. Concerning it our knowledge is in a most 



unsatisfactory condition. With regard to the former genus we do not 



possess a good description of any species, although these are abundant 



in northern and southern seas. Consequently the definition given 



above must be considered provisional. Already Enterostoma striatum, 



v. Graff, has been investigated, with the result that Bohmig places it 



under the sub-family Cylindrostomince (loc. cit., p. 469), and similar 



change in species hitherto considered as belonging to the Allostomince 



may be expected to result from detailed investigations. 



Genus 19. — Enterostoma, Claparede (35). 

 Allostomince with uniformly ciliated body and without a circular " ciliated 

 groove " on the head. 



44. Enterostoma austriacum, v. Graff. PI. X, fig. 7. 



Length *75 mm. Body rounded anteriorly, tapering to a blunt 

 " tail " behind. Colour usually yellow, with a black spot (due to the 

 intestine) in the centre ; occasionally the general colour is white, the 

 gut being yellow. The colour of the surface is due to the presence of 

 yellow granules in the epidermis ; that of the gut to its contents. 

 The yellow epidermal granules are massed together in small heaps, 

 which are not so conspicuous or large as figured by v. Graff (pi. xix, 

 fig. 9, Monograph). Exceedingly small, slender rhabdites are present 

 in groups in the epidermis. The pharynx is cylindrical, very muscular, 

 and is inserted at the hinder edge of the extensive gut, which, 

 following the outline of the body, reaches as far forward as the brain. 

 The eyes are arranged in two pairs, an anterior and a posterior pair. 

 The former are slightly the smaller, and their lenses are directed 

 outwards and backwards ; the lenses of the posterior pair face forwards 

 and outwards. The genital aperture is a short distance from the 

 hinder extremity. Round the brain are the developing testes. The 

 pyriform muscular penis lies behind the pharynx. 



