A NEW FRESHr WATER NEMERTINE. 



243 



As to histological characters of the frontal and cephalic organs, 

 I have found nothing peculiar to the present species. The same may 

 be said of the central nervous system and also of the number and 

 distribution of the cephalic nerves. Only there exists a not un- 

 important point of deviation from Böhmig' s description for St. gracensc, 

 with respect to the origin of that cephalic nerve which distributes it- 

 self to the cephalic organ. According to him, the nerve in question 

 originates from the frontal surface of the dorsal ganglion. This is 

 decidedly not the case in the present species ; here, that nerve arises 

 from about the middle of the posterior surface of the said ganglion and 

 turns round the outer ventral side of it to join the bottom of the 

 cephalic organ. 



As was pointed out by Böhmig in St. gracensc, the lateral nerve- 

 stems contain very fine muscle-fibres imbedded in the substance of the 

 nervous tissue. In contrast to the muscle-fibres being in that species 

 variable in number, they are in the present species so definite in number 

 and position that there are constantly 2 of them to be found in every 

 part of the stem, always lying in the inner dorsal part of the fibrous 

 layer. I have not been able to trace, as Böhmig did, these muscle- 

 fibres passing out of the brain to the proboscis-musculature. It seems 

 to me probable that they do not do so at all but end in the brain. 



One word with reference to the vascular system. This in the 

 present species may be saiJ to agree well with that of St. gracensc. 

 Accordingly, I have found the very same junction between the dorsal 

 and the right lateral vessels as that which was described and figured 

 by Böhmig from St. gracensc. The junction occurs just behind the 

 dorsal commissure of the brain. 



As to the distributional range of the excretory organs, the present 

 species agrees with the others already known. In fact, they are- 

 present nearly throughout the whole length of body, extending from 

 in front of the brain to the posterior body-end. I have not yet 

 examined a sufficient number of specimens to be able to give the 



