450 F. W. GAMBLE. 



proboscis provided with numerous circular folds. The base of 

 the proboscis is marked oflF by a tuft of cilia on each side. A 

 single posterior group of setae at the hinder end. The posterior 

 sixth of the body is marked off transversely (probably an 

 indication of fission). 



Habitat. — Coast of Skye (Claparede). 



Claparede (35) described this form as a rhabdocoele larva^ but 

 it was referred to Alaurina by Metschnikoff (37). It is 

 probable that this genus is not uncommon on our coasts. 



Family MESOSTOMID^. 

 Rhabdocoela with one or two genital apertures; 

 yolk-glands and germaria distinct or united. 

 Testes compact. Female accessory organs present. 

 Pharynx ventral, rosulate (for the term '^ rosulate " 

 see V. Graff, ' Monogr./ p. 80). 



Subfamily Promesostomin^. 

 Genus 7. — Promesostoma, v. Graff. 

 Mesostomidse with two germaria and separate yolk- 

 glands, and a common genital aperture. Female 

 accessory organs absent. Testes small. 



10. Promesostoma MARMORATUM (Schultzc [27]). PI. XXXIX, 

 fig. 10; PI. XL, fig. 16. 



Length '5 — 1'5 mm. Body elongate, cylindrical, broadly 

 rounded in front, truncate behind. Anterior end used as a 

 tactile organ. Colour very variable. The epidermis which 

 furnishes the ground colour is colourless, bright yellow, or 

 yellowish-red. Black reticular pigment is almost constantly 

 present as a small patch between the e}es; elsewhere to 

 a variable extent, and may be entirely absent. The epidermis 

 on the inner side of the eyes contains immense numbers of 

 rhabdites (fifteen to twenty in a single mother- cell), forming 

 two well-defined tracks. Elsewhere they are few in number. 

 The posterior end is provided with adhesive papillae. 



