NEMERTEANS 



279 



Anatomy. A feature of the sections throughout the body is the thickness of the base- 

 ment membrane (Fig. 55) which is rather thicker than the epithelium. Both circular and 

 longitudinal muscles are strongly developed. I could not be certain of the presence of 

 head glands owing to the peculiar staining of the head, but there appears to be a thick 

 strand staining deeply with haematoxylin dorsal to the rhynchocoel. The proboscis has 

 fourteen nerves and is armed with a main stylet on an elongated pear-shaped base 

 0-098 mm. long and two reservoirs each with two stylets. The frilled mouth is a con- 

 tinuation of the stomach into which the narrow folded tube expands after the brain. 



Fig. 54. Tetrastemma weddelli, n.sp. A, outline 

 sketch of the preserved specimen, x 3 approx.; 

 B, graphic reconstruction of the anterior end. 



Fig. 55. Tetrastemma weddelli, n.sp. Transverse 

 section across the body, bm, basement membrane; 

 cm, circular muscles; ep, epithelium; hn, longi- 

 tudinal muscles;/), proboscis. 



There is a single forward diverticulum of the gut which is lateral to the stomach and 

 does not reach the brain. The excretory tubules open dorso-laterally above the lateral 



nerves. 



There are two pairs of eyes. In this specimen there is a double eye on one side. The 

 brain is large and the dorsal ganglia are far larger than the ventral. The ganglia of each 

 side are close together, especially the ventral ganglia at the anterior end (Fig. 54B), so 

 that the ventral commissure is very short. There is a dorsal strand in the lateral nerves. 

 The cerebral organs are large and lie along the dorsal ganglia. They open laterally from 

 their posterior ends, though whether this is connected with the pushing forward of the 

 alimentary canal or the normal position in life I am unable to say. 



The specimen was a male with ripe sperm. 



