218 F. W. GAMBLE, B.SC. 



the arrangement of these bands, which he observed in a single 

 gathering among Ulva at Millport ; and this does not exhaust the 

 possible cases. Small specimens ("5 — 1 mm.) with a yellow ground- 

 colour (due apparently to the contents of the gut-cells) are not 

 uncommon. Since the "key" for the determination of species of this 

 genus in v. Graff's Monograph is largely dependent on the arrangement 

 of the pigment, these varieties are at first very troublesome. More- 

 over Vorticeros auriculatum (which frequently occurs among Plagiostoma 

 vittatum) with retracted tentacles, can be in no way anatomically 

 distinguished from a common variety of Flag, vittatum, in which the 

 pigment is present over the greater part of the dorsal surface. With 

 regard to the internal anatomy I can confirm the accounts of v. Graff 

 and Jensen (49). Van Beneden (33), the first to discover the stalked 

 yellow-brown egg-capsules, found them attached to the abdominal feet 

 of the lobster. At Plymouth they were abundant in September on 

 the sides of a vessel containing several individuals. 



Habitat. — Apparently more abundant on our northern than 

 southern coasts. Millport, abundant (v. Graff) ; Plymouth ; Port 

 Erin, Isle of Man (F. W. G.). 



Distribution. — Faroe Islands (Schmidt), Bergen (Jensen), Heligo- 

 land (Leuckart, 23), Walcheren, on coast of Belgium (Slabber),* 

 Ostende (van Beneden), Wimmereux (Hallez). 



38. Plagiostoma korbni, Jensen. 



Length 1*4 mm. Body similar in shape to Plag. vittatum, but 

 smaller, and rather narrower in front. The first half of the body is 

 white, and behind this a broad transverse brown band (due to reticular 

 pigment) over the dorsal surface and the sides. Behind this again are 

 scattered brown spots. The brain, which bears two red eyes, is placed 

 in front of the spherical pharynx and mouth. The remaining anatomy 

 has been investigated by Jensen (49), whose figures (pi. v, figs. 1 — 8) 

 are highly characteristic. 



Habitat. — On the inner side of the Breakwater, and elsewhere 

 among algae between tide-marks, Plymouth Sound (F. W. G.) ■ a 

 specimen at Millport (v. Graff). 



* ' Physikaliache Belustigungen,' Nurnberg, 1775, pp. 31 and 36. 



