NEMERTEANS 



253 



An investigation was made of the length of the mouth and of the cephalic slits relative 

 to the body length in the preserved specimens with the interesting result that the ap- 

 parently very large mouth of type (ii) is actually smaller for the length of the animal 

 than it is in either of the other types. 



Internal anatomy . Frontal organs are present. The head glands are thin and scattered. 

 They stain with haematoxylin and near the tip of the head are grouped into three areas. 

 They do not reach the brain. The vascular and nervous systems have been well described 

 by previous authors. In the rhynchodaeum there are outpushings noted by Joubin and 

 considered by him to connect the blood lacunae with the exterior. Although they pro- 



.Iki 



A 



mi 



olm $g£&9i# 



B 



D 



Fig. 26. Litieus corrugatus, Mcintosh. The dorso-lateral epidermal layers in transverse section. Reference 

 letters as in Fig. 25. bm, basement membrane; c, cutis; e, epithelium;/?, fibrous layer; olm, outer longi- 

 tudinal muscles. 



trude into the lacunae I have not been able to find any gap in the intervening tissue that 

 would suggest free communication. These outpushings vary in number but have been 

 seen in all types (Fig. 24). 



The divergences in the anatomy of the three types are connected with the relative 

 position of the organs (Fig. 25) and in the gland cells of the cutis and the cutis itself. 

 Fig. 26 shows the forms of the dorso-lateral cuticular layers at the level of the anterior 

 end of the mouth. Type (i) possesses the thick muscle-free basement membrane of 

 Cerebratulus charcoti, and of C. corrugatus as described by Burger (1904, p. 96); type 

 (iii) the thinner layer with circular fibres of C. steinini. A second series of type (i) shows 



