I 1 8 NEMERTINEA CHAP. 



The species which was discovered by Willemoes-Suhm, and 

 named by him Tetrastemma agricola,li\es under stones in damp 

 earth in the Bermudas. It differs from the other two in that 

 the proboscis opens by a special terminal aperture. It measures 

 nearly an inch and a half in length, and, like G. chalicophora, is 

 milk-white in colour. It resembles it also in possessing four 

 eyes, and in the absence of cerebral organs and cephalic slits. 



Fresh-water Forms. In most cases the descriptions of 

 fresh-water forms are so vague and incomplete that it is difficult 

 to determine whether or not they are different species. 



They are probably more numerous than is at present known, 

 and are certainly scattered widely over the face of the earth, since 

 they have been found in Nicaragua, at Tashkend in Turkestan, 

 and at Philadelphia and Monroe in the United States. 



A form of which we have a full description is Tetrastemma 

 aquarium dulcium, found by Silliman l at Monroe, under stones 

 in brooks in company with Planarians. It is a small worm of a 

 red or pink colour, about half an inch in length, and it possesses 

 usually three pairs of eyes. The proboscis is armed, and opens 

 by a separate aperture. The excretory system consists of a 

 vessel on each side of the body, each opening externally by a 

 pore, and internally dividing into numerous branches which end 

 in ciliated expansions. An individual of the same species was 

 Found by Beddard in one of the tanks in the Botanical Gardens in 

 Regent's Park, but as the tank is one in which tropical plants are 

 grown, it had almost certainly been introduced among the roots 

 of the plants, and cannot be considered as a British species. 



A fresh-water Nemertine belonging to the genus Tetrastemma 

 was, however, found by Benham 2 on the roots of some water 

 plants in the Cherwell at Oxford. The specimen was of a bright 

 orange colour and measured half an inch in length. 



Du Plessis 3 found another fresh- water form on the lower 

 surface of stones in shallow pools on the shores of the Lake 

 of Geneva, and named it Tetrastemma lacustre. It is a small 

 animal, the largest specimens being rather over an inch in length. 



Another European genus was found in 1893 by F. E. Schulze 

 in Berlin. It has been fully described by T. H. Montgomery, 4 who 

 has given it the name of Stichostemma eilhardii. 



1 Zcitschr. wiss. Zool. Bd. xli. 1885, p. 48. 2 Nature, vol. xlvi. 1892, p. 611. 

 3 Zool. Anz. vol. xv. 1892, p. 64. 4 Zcitschr. wiss. Zool. Bd. lix. 1895, p. 83. 



