14 R'. C. Punnett. [No. 2 



those found in Carinella. The oesophageal plexus is not very 

 distinct and ends with the excretory system. 



The excretory system is built up on the usual Heteronemertean 

 plan. Towards its posterior end there is present a single duct 

 on either side (Pl. I, fig. 4). The tubules are found almost entirely 

 dorsal to the level of the nervous side st ems. 



The gonads alternate regularly with the gut pouches. All the 

 specimens obtained were immature and no ducts were to be 

 found. 



The nervous system is well developed, the brain, compared with 

 size of the worm, being exceedingly large. The dorsal 

 ganglion is somewhat larger than the ventral and the dorsal 

 commissure is very strong. The median dorsal nerve is conspicu- 

 ous. In the region of the brain, and also a little in front of it a 

 number of small ganglion cells occur massed round the head 

 slits. Very large ganglion cells (neurochord cells?) occur both 

 in the dorsal and ventral ganglion. The cerebral organ is well 

 developed and exhibits the usual Heteronemertean structure. 



The frontal organ is either exceedingly small or absent alto- 

 gether. The head glands are very feebly developed. No eyes 

 present. The head slits are very shallow though owing to the 

 very large size of the brain they almost reach to it. A few 

 words on the affinities of L. vivens may not be out of place 

 here. Within the last two years two interesting new forms, 

 Zygeupolia and Micrella have been brought to light, the ana- 

 tomy of which throws new light on the affinities of the 

 Heteronemerteans. These new forms are undoubtedly the most 

 primitive members of the order in many respects and serve to 

 link the Heteronemerteans more closely with the Protonemer- 

 teans. In any attempt to derive the former group from the 

 latter certain structural stages must be postulated, assumptions 

 which derive support from the anatomy of the two genera 

 mentioned. And in certain respects L. niveus approximates 

 more closely to Zygeu\iol\a and Micrella than to most of the 

 other members of the order. 



As is well known the Heteronemerteans are characterized 

 by the possession of a glandular cutis and an outer layer of 

 longitudinal muscles beneath which lie the nerve stems. In 

 a Protonemertean such as Carinella the body wall external 

 to the basement membrane consists only of a thick epithelium 



