1900.] NESLERTEAyS FROM TOEEES STBA1TS. 829 



Cebebeatultts haddoni, n. sp. (Plate LV. figs. 7 a-e, 8, & 9.) 



About 5 cm. of fragments of a single specimen from Thursday 

 Island. The oesophageal region is round and about 6 mm. in 

 diameter. In the intestinal region the breadth is about 8 mm., the 

 depth being 5 mm. The mouth is large. The head-slits extend 

 backwards to the level where the mouth commences. Colour in 

 the preserved state whitish grey, covered with darker mottlings 

 except on the snout. 



The epithelium in the oesophageal region contains a few large 

 granular cells (Stabchenzellen) in its deeper portion. There is no 

 well-marked basement-membrane. The cutis presents the fine 

 circular and longitudinal muscle-fibrils. The cutis-glands are poorly 

 developed. The connective-tissue layer (fig. 8, cu.) is very strong, 

 being almost as thick as the powerful external longitudinal muscle- 

 layer. It contains a very few muscle-fibrils. 



The muscle-layers are all well developed. 



The vascular system shows a well-marked head-loop. 



The proboscis is of moderate size, but presents no muscle- 

 crosses. 



The proboscis-sheath contains the usual outer circular and inner 

 longitudinal muscle-layers. The latter is more strongly developed 

 ventrally than dorsally. 



The alimentary canal possesses a wide, shallow, ventral gutter in 

 the intestinal region. 



The excretory system starts some way behind the mouth and 

 extends over about 2 mm. in the preserved specimen (fig. 9). I 

 have been able to observe no openings to the exterior \ The 

 oesophageal vascular lacunae are very small. The excretory tubules 

 lie wholly ventral to the level of the side stems. 



The yenerative sacs are small, numerous, and scattered in the in- 

 testinal region, thus not conforming to the usual arrangement, in 

 which there is a single sac between each successive pair of intestinal 

 pouches. Apparently the ducts are not yet developed. 



In the nervous system the brain presents no special features. 

 Neurochord-cells are not present at the level of the ventral com- 

 missure. The median dorsal nerve is not distinguishable from the 

 rest of the nervous sheath surrounding the circular musculature. 

 An inferior median dorsal nerve, lying just above the proboscis- 

 sheath, is well marked in this species. 



The cerebral organ is seen in section before the separation of the 

 dorsal and ventral lobes of the dorsal ganglion (fin. 7 b). It is 

 invested by gland-cells only on its ventral surface. 



The head-slits are deep, reaching almost to the brain. Externally 

 they end abruptly before the level where the cerebral organ 

 commences (fig. 9). 



Eyes and frontal organ are both absent. 



The head-glands are very scanty and end early. 



1 Cf. C. robustus (Punnett, 6), which this species greatly resembles with regard 

 to its excretory and vascular systems. 



