24 



THE VOYAGE OF H.M.S. CHALLENGER. 



them and encircles the proboscis. From the lobes depart the two lateral nerves (n) and 



some other cephalic nerves, which were not quite clearly visible The cephalic 



fissures or ciliated sacs .... 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 semicircular opening of the 

 mouth (o) leading into an intestinal tube (i), which runs through the whole length of the 



animal, without showing anything particular, and is terminated by an anus (a) 



The proboscis is divided into two portions — 

 the papilligerous part and the glandular part. 

 At the bottom of the former we find a peculiar 

 spine .... 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 3 ), 1 whde in 

 the female the base has sharpened angles (fig. 

 3, pr*). 1 I do not think that such sexual 

 differences have hitherto been observed in 

 Nemerteans. 



" The ovaries and testes are, as usual, situ- 

 ated between the intestine and the walls of the 



body I . . . . establish 



for it the specific name of agricola, as 

 there is probably no described marine species 

 of Tetrastemma with which it could be 

 identified. 



" I, however, do not attach much import- 

 ance to this point, as the object of these lines 

 is only to show that in America also land 

 Nemerteans exist. Hitherto they were only known from the Pelew Islands, where 

 Semper has found another, to which he has given the name of Geonemertes palseensis. 

 I think it is highly probable that land Nemerteans exist to a greater extent in tropical 

 countries than has hitherto been supposed, and that from their hidden life, and the 

 impossibility of preserving them, they have hitherto escaped the attention of travelling 

 naturalists. Especially in such islands as the Bermudas, where the earth of the lower 

 grounds contains a great deal of salt, it may easily be imagined how marine animals have 

 taken to terrestrial habits ; and it was interesting for me to see that one Tetrastemma 



1 These figures referred to by Suhui have not been here reproduced. 



Fjg. 2. — Tetrastemma agricola, Willemoes Suhm. o, mouth ; 

 g, brain; n, lateral nerve; i, intestine; Pt 1, rhyn- 

 cnodteum ; Pt 2, papuliferous ; Pt I, glandular part of 

 the proboscis ; Pt 3 and ca, region of the stylet and 

 reservoir. 



