410 Dr. R. V. Willemoes-Suhm on a 



granules together, in which, however, a regular lens could not 

 be observed. Underneath these eyes is seen the prominent 

 centre of the nervous system (PI. XVII. fig. 1, ^) : it consists 

 of two lobes, and a ring which connects them and encircles 

 the proboscis. From these lobes depart the two lateral nerves 

 (fig. l,w), and some other cephalic nerves, which were not 

 quite clearly visible. In most genera of the Tremacephalidse 

 the cephalic fasures or ciliated sacs are easily to be seen ; here 

 they are either very small or wanting entirely. Sometimes a 

 folding of the skin seemed to indicate their presence ; but in 

 the contractile bodies of these worms it is very difficult to say 

 whether you have a small cephalic fissure or a folding of the 

 skin before you. 



Underneath the ganglion, on the under surface is the semi- 

 circular opening of the mouth (fig. l,o), leading into an in- 

 testinal tube (fig. 1,«), which runs through the whole length 

 of the animal without showing any thing particular, and is 

 terminated by an anus (fig. 1,«). It is covered above by a 

 \ong proboscis (fig. 1, pr^-p>r'^), which opens at the front and 

 ends in the posterior part of the body, where its thin termina- 

 tion is attached to its walls. This proboscis is divided into 

 two portions — the papilligerous part, and the glandular part. 

 At the bottom of the former we find a peculiar spine, the top 

 of which is supposed to be renewed from the smaller spines 

 which are in store in two vesicles on each side of it. This 

 spine is remarkable, because it differs in form according 

 to the sex of its owner. In the male it has a rounded base 

 and is pear-shaped (fig. 2, pr^)^ while in the female the base 

 has sharpened angles (fig. 3,^r^). I do not think that such 

 sexual differences have hitherto been observed in Nemerteans. 



The ovaries and testes are, as usual, situated between the 

 intestine and the walls of the body. They did not present 

 any thing peculiar, and are not represented in the diagram- 

 matic figure I have often refeiTed to. Probably the animal is 

 viviparous, as is Tetrastemma ohsourum from the Baltic ; but 

 on this subject nothing has been observed. 



Though I have not been able to demonstrate the cephalic 

 sacs, which are peculiar to most of the Tremacephalidae 

 hitherto described, I think tliere can be hardly any doubt that 

 this worm belongs to that family ; for some marine species of 

 the genus Tetrastemma bear a most close resemblance to it. 

 I therefore think I can safely call it by this latter generic 

 name, and establish for it the specific name of agricoluy as there 

 is probably no described marine species of Tetrastemma with 

 which it could be identified. 



I, hov/ever, do not attach much importance to this point, as 



