262 



DISCOVERY REPORTS 



traction twist when they become the lateral nerves. No dorsal strand could be detected 

 in the lateral nerves. The cerebral canals are short. Their openings are ventro-lateral. 

 The organs themselves are large and at first closely applied to the sides of the dorsal 

 ganglia. Fibres from the ganglia pass into them and form the only connection. They 

 shift ventrally, wedging themselves between the dorsal and ventral ganglia. On the dis- 

 appearance of the dorsal ganglia the organs also diminish and end. Fig. 35 shows the 

 relative positions of the various organs in the head from a graphic reconstruction. 

 Reference to Fig. 37 will show how closely the main anatomical features of this species 

 resemble those of A. marioni, allowing for the greater degree of contraction in the latter 

 and the fact that the proboscis is considerably thicker. In Fig. 36 outline drawings of 

 spirit specimens of the four species are given illustrating the differences in shape of the 

 body. A. lecointei should be easily recognized in life by its distinctive form and colour. 



Amphiporus marioni, Hubrecht, 1887 (Figs. 36 A, 37, 38). 



One specimen (N 5) was taken from a kelp root from King Edward Cove. It was 

 not sketched until the following day when it was sorted from A . moseleyi with which it 

 had been fixed. The colour and general appearance are probably very similar. The 

 length was 9-3 mm., the breadth 1-5 mm. (in spirit). 



The small stoutly built body is flattened posteriorly. No eyes can be seen (Fig. 36A). 



Anatomy. In the region of the stomach the longitudinal muscle layer is three or four 

 times as thick as the epithelium. Farther back down the body it is less than twice as 

 thick and in some positions — mid-ventrally under the gut and mid-dorsally— it is 

 thinner than the epithelium. The basement membrane is very thick and appears fibrous. 



The head glands are large and compact. One 

 strand, dorsal to the rhynchocoel, opens by a pore 

 ventral to the tip of the snout. This strand does not 

 reach the dorsal commissure. There are two lateral 

 strands, one on each side of the rhynchocoel, which 

 extend back ventral to the brain as far as the ventral 

 commissure and opening of the cerebral canals 

 (Fig. 37). There are cerebral subepithelial glands on 

 each side from the tip of the head to the cerebral 

 organs. About fifteen eyespots with very light brown 

 pigment are present on each side. 



The oesophagus opens into the rhynchodaeum 



before the brain and at the level of the cerebral 



organs it becomes the stomach. The anterior caecum 



is much branched and the branches extend forwards 



and approach the posterior end of the brain. The 



lateral diverticula of the gut extend above the lateral „. „ , . . . „ , , „ 



fig. 37. Amphiporus marioni, Hubrecht. 



nerves (Fig. 38). The proboscis is thick. There are Graphic reconstruction of the anterior 

 fifteen nerves. The armature consists of a main stylet end of the body. 



