154 Marine Inccst'ujations in South Africa. Vol. V. 



Colour. — A pure white pigment of finely branching chromatophores 

 occurs in spots irreguhirly placed on the tentacles. These spots were 

 somewhat elongate in the direction of the length of the tentacles. 

 To the naked eye each appears as a solid spot, but when examined 

 with a lens is seen to be more or less divided longitudinally, and to 

 consist in reality of two patches, one on each side of the tentacle. 

 At the base of the tentacle they are more numerous, and form a 

 continuous line along the lophophore near the oral region so as 

 to form an incomplete circle. At the median point (that is, the 

 mouth region) a strip of pigment passes backwards towards the 

 anus (or along the dorsal aspect of the animal), and ends in a 

 slightly enlarged circular patch. Whether or not this spot coincides 

 with the anus, as it appears to do, could not with certainty be made 

 out as the pigment was not visible in sections. The white pigment 

 extends on to the body in few and irregular streaks below the 

 lophophore. 



Apart from this pigment the tentacle and lophophore were clear, 

 transparent, and apparently colourless. The body, however, was of 

 a faint yellowish colour. 



Nervous System. — The single nerve along the left side of the 

 body is well developed. The nerve cells are numerous and well 

 developed, and are arranged so as to form a solid rod (of. Caldwell (3), 

 Cori (4), Longchamps (8). A transverse section showed that this nerve 

 is not hollow, the centre being occupied by a clear, refractile, non- 

 staining substance. The nerve was thus, as a whole, partly 

 differentiated from the epithelium, but not sinking away from it. 



In following the sections upwards however it is seen that as they 

 approach the duct of the nephridia the nerve gradually leaves the 

 epithelium of the body, and when the duct (double, as it is here in 

 the form of a loop) is cut the nerve is seen internal to it. Succeed- 

 ing sections show that, after the nerve has thus passed over the duct 

 on the inside, it again passes out between the two limbs of the duct 

 before joining the circum-oesophageal ring of nerve tissue ; in other 

 words, on coming to the nephridial duct it passes over it on the 

 inside in place of continuing on the outside, where the epidermis of 

 the body is. This twisting of the lateral nerve may be associated 

 with the marked distortion of the body. The anus, at one time 

 terminal, has come to lie near and behind the mouth. The 

 nephridial opening, at one time probably ventral and below the 

 lateral nerve chord, has been carried upwards, necessarily passing 

 over the lateral nerve chord, and finally attains a position near 

 the anus. 



The passing of the opening of the nephridial duct over the nerve 



