EEPORT ON THE NEMERTEA. 23 



situated at the posterior extremity ; the longitudinal canal is anteriorly very copiously 

 branched (PI. X. fig. 1, Nej)). 



There is a very thick basement membrane {B) to the integument, and very strongly de- 

 veloped gelatinous tissue {Gt) inside the muscular body- wall. Curious granular enclosures 

 {inc) occurring in this tissue, both in the head and in the body, will be elsewhere described. 



The longitudinal nerve-trunks are not wholly lateral but nearly so; there are no 

 ventral commissures between them. 



The generative cseca assume the ordinary character of paired dorsal receptacles meta- 

 merically distributed between the intestinal cseca. The generative pores are dorsal and 

 situated above the nerve-trunks. 



The ova, present in. both specimens, are in both of them characterised by a curious 

 refractive body constantly present in addition to the nucleus, and staining deeply 

 with picrocarmine. This " ^aaranucleus " can be seen to be present at the very earliest 

 stages of the development of the eggs which came under observation ; stages at which 

 the eggs could still hardly be distinguished from the surrounding cellular elements in 

 the wall of the generative ceeca (PL XV. figs. 14, 15). 



Family Tetkastemmid^. 

 Tetrastemma, Ehrenberg. 

 Eyes four ; arranged so as to indicate a square or oblong. Specimens generally small. 



Tetrastemma agricola, Willemoes Suhm. 



Of this species, collected by Suhm in Bermuda (Mangrove swamps, Hungry Bay) and 

 which is the only Land Nemertean procured during the voyage, no specimens have been 

 preserved, although Suhm tells us that he collected a good many of them. So I must 

 content myself with reproducing the chief points of its anatomy as they were made out 

 by him in the Ann. and Mag. Nat. Hist, for June 1874. At the same time I have repro- 

 duced one of his figures in woodcut. Suhm writes {loc. cit., p. 409): — 



" The largest of these worms have a length of 35 mm. by 2 mm. in width. They are 

 of a milky-white colour. Their movements are slow and sometimes eatterj)illar-like ; 

 they shoot out their long proboscis, fix it at some distant point to which it adheres by 

 means of its papillae, and draw their body after them. Their skin is filled with rod-like 

 bodies as described by Max Schultze and others, and is covered on the outside all over 

 with cilia. In the front we find two pairs of eyes, one of them near the entrance of the 

 proboscis, the other smaller one further out ; they consist of a fine granulated pigment, 

 imbedded in a colourless substance, which holds these granules together, in which, how- 

 ever a reo-ular lens could not be observed; underneath these eyes is seen the prominent 

 centre of the nervous system (fig. l,g); it consists of two lobes and a ring which connects 



