A NEW FRESH-WATER NEMERTINE. 241 



cuous marginal constrictions (m. c.) lying a short way behind the 

 dorsal ganglia (d. g.) and reaching to some extent the dorsal side of body. 



The adult (fig. 1) always shows a bright yellowish red colour 

 which becomes gradually fainter towards both extremities of the body. 

 For a comparatively long period after hatching, the young are 

 simply milky white; as in Stichostemma gracense when grown to 

 a length of 2-3 mm., they acquire a light rosy-red colour. In later 

 stages of growth, the red colour becomes gradually deeper, and at 

 the same time there occurs a new deposition of a dark-green pigment 

 in the form of finely granular spots. These spots increase in number, 

 becoming more and more closely distributed, until the worm attains a 

 length of about 10 mm. Thenceforth, while the red continues to 

 deepen, the green pigments become on the contrary fainter and fainter, 

 finally to disappear altogether when the animal is about 15 mm, 

 long. In sexually mature individuals there are two longitudinal series, 

 one on each side, of small roundish markings of an ochre -yellow 

 colour (indicated in fig. 1). They are due simply to the presence 

 of mature gonads, each containing several eggs of a yellowish colour. 



Even in the fresh state, the proboscis can be detected through 

 the skin as a narrow opaque streak running posteriorly for about 

 three-fifths of the body-length (see fig. 1). Of course, this apparent 

 length does not cover the actual extent of the whole organ, since 

 the rhynchocoel, when traced by means of sections, arc found to 

 extend as far back as the beginning of the posterior one-third of the 

 body. 



The entire surface of the worm is uniformly ciliated. Sensory 

 spines, such as occur in Stichostcmma gracense^ are not present. 



Internal characters. 

 The stomodaium and the rhynchodaeum are united into a common 



1) Böhmig, L., Beiträge zur Anatomie und Histologie der Nemertinen (St. gracense 

 Böhmig, ü eonc mer les chalicofhora Graff), Zeitschr. f. Wiss. Zool., Bd. 64, 1898. 



