362 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



the reddish brown pigment so abundant in the shore form, 

 while others had obscure patches similar in disposition to 

 those present in the latter but much paler in colour. 

 Minute flakes of opaque yellowish white were scattered 

 all over the surface of the body as in the shore form, and 

 in many cases a concentration of these along the mid- 

 dorsal line produced a pale longitudinal streak. The 

 white flakes in this species are more superficial than the 

 reddish brown pigment. The latter is in the form of 

 much branched pigment cells whose processes run for the 

 the most part in the direction of the long axis of the body. 



Tetrastemma nigrum, Riches. 



A few examples of this species were met with both in 

 1894 and 1895. They were found in weeds from Port 

 Erin shore and from the Clets in the Calf Sound, and 

 were from 5 to 15 mm. in length. 



Joubin, who does not appear to have met with this 

 form, expresses doubt as to its being specifically distinct 

 from Tetrastemma dor sale. In shape, in the character of 

 its stylet apparatus and other anatomical details, it does 

 certainly agree with the latter, but so long as colour is 

 relied en for the discrimination of the species of Tetras- 

 temma, it must be regarded as a well marked species, 

 much more so for example than are T. candidum and its 

 allies. 



In Tetrastemma nigrum the warm buff ground colour 

 is in most cases almost entirely concealed by black, or 

 almost black, reticular pigment, which is totally different 

 in character from anything seen in T. dorsale ; while on 

 the other hand the branched reddish brown pigment and 

 opaque white flakes so characteristic of the latter are 

 entirely absent in T. nigrum. 



Though Tetrastemma nigrum varies considerably, the 

 variation met with merely concerns the extent to which 



