274 



DISCOVERY REPORTS 



cerebral organs could be seen and the eyes and enormously developed head glands, 

 though the latter did not stain as they had in the free specimens. The lateral nerves had 

 degenerated considerably and the body consisted of a thin investment of basement mem- 

 brane and muscles and a large amount of internal structureless substance in which the 

 gut walls could still be recognized. No genital products could be seen. A specimen of 

 T. gitlliveri taken from red algae off the Point in King Edward Cove in March 1930 

 was full of eggs, so that there is evidence of a form of hibernation in this species. 



Tetrastemma hansi, Burger, 1893 (Plate XVI, figs. 6, 15; Fig. 50). 



This species was first collected from the kelp roots in King Edward Cove in October 

 1925. Thirteen specimens were taken, sketched and noted (N 12). In March 1926 seven 

 specimens differing in colour and body form were collected and described under N 17. 

 These were later proved from their anatomy to be identical with the earlier forms. In 

 April 1927 many specimens were collected of intermediate size and covering the range 

 of colour. In November 1927 a specimen was taken that contained nearly ripe gonads 

 visible through the ventral surface of the body. 



Several small immature specimens were collected at St. 53 (Falkland Islands) and 

 identified from sections (N 106). 



Form and colour in life. The length and breadth rarely exceed io-o and i-o mm., 

 though the breadth may be less for the same length. The body is round ; the head just 

 visibly marked from the body by its greater width. There are two lateral grooves on each 

 side of the head and two pairs of eyespots. The head 

 tapers to an acute snout. The colour varies from very 

 light brown through shades of yellow-brown to light 

 red and pink. There are sometimes traces of a pale 

 median line down the back, not visible near the head 

 and fading before the tail. Ventrally the animals are 

 pale. 



Form and colour of preserved specimens. The body 

 is round in section, about 8 mm. long and 0-5 mm. 

 broad. The head is blunter than the tail. The colour 

 is completely bleached and the eyes are only visible 

 faintly in the smallest specimens. On clearing the 

 small proboscis can be seen not reaching to half the 

 length of the body. The eyespots are very small. 



Anatomy. The epithelium is very thick; the base- 

 ment membrane and circular muscles very thin and 

 equal in thickness. There are eosinophile gland cells 

 beneath the longitudinal muscle layer ventral to the 

 brain. The head glands are extremely developed though 

 they do not stain with haematoxylin. They fill the head Graphic reconstruction of the head, 

 and stretch back beyond the brain and the two forward hg, head glands. 



