92 mr. it. c. pumrBTO ox [^ a y 21, 



The alimentary canal presents no peculiar features. The most 

 anterior pair of the blind-gut diverticula do not reach to the 

 brain. The oesophagus opens into the rhynchodaeum about half- 

 way between the tip of the snout and the commencement of the 

 brain. The proboscis-sheath extends back to the posterior 

 extremity of the body. 



The proboscis is well developed. Its armature consists of a 

 central stylet 210 ^ in length attached to a rather shorter base, 

 185 /j. long. There are two pockets of reserve stylets each con- 

 taining 4. A somewhat remarkable variation ] occurs in the number 

 of the proboscis-nerves. Whilst the females show 12 nerves in the 

 proboscis, the males may have either 12, 17, or 18. The excretory 

 system resembles that usually found in the genus. The branched 

 tubules commence just behind the cerebral organ and extend 

 backwards for several mm. (Plate VII. fig. 8). There is a single 

 excretory pore on either side shortly behind the brain ; it opens 

 laterally and somewhat ventrally. 



The gonidial sacs are numerous and irregularly arranged. Both 

 ova and spermatozoa are almost or quite ripe. 



The nervous system shows no marked peculiarities. Shortly 

 after its commencement the dorsal ganglion gives off laterally a 

 nerve to the cerebral organ. A small median dorsal nerve is 

 present. There is a supra-anal nerve commissure posteriorly. 



The cerebral organs are well developed and lie for the most part in 

 front of the brain. Seen in transverse section, their height some- 

 what exceeds their breadth (av. height 350 fi, av. breadth 250 yu). 

 Their opening is in front of the brain about \ of the distance 

 between the anterior extremity of the brain and the tip of the 

 snout (Plate VII. fig. 8). 



Numerous eyes are present, amounting to about 40 on each side. 

 They are arranged as a row from the tip of the head to the anterior 

 brain-region, where they form a cluster. 



Scanty head-glands are present opening ventrally. 



Amphipobus pauli>ts, n. sp. (Plate VII. fig. 11.) 



Several specimens collected by Prof. D'Arcy Thompson in the 

 Pribyloff Is., Behnng Straits. In external form a long slender 

 species tapering at either end. The specimens varied in length 

 from about 50-90 mm. In a specimen 90 mm. long the greatest 

 breadth was 4 mm. — which proportions in the preserved state 

 point to this species being longer and more slender than most other 

 members of the genus. Colour after preservation a pale yellowish 

 brown dorsally and almost white ventrally. There are no distinctive 

 markings. 



The epithelium is high, and rests upon a comparatively thin 

 basement-membrane (about 18 \i thick). 



The circular layer of the muscular system is rather thicker than 

 the basement-membrane. Ventrally there is a thin diagonal layer 



1 See note on p. 104. 



