520 W. a. Coe — JSTew Palceonemerteans. 



circular and outer longitudinal layers increase in thickness. A sec- 

 tion through the posterior third of the proboscis, therefore, shows 

 only an inner circular, and an outer longitudinal layer of muscles. 



The epithelium of the cesophagus is composed of an outer layer of 

 ciliated cells with gland-cells beneath. The musculature is thin but 

 is easily made out. The intestinal caeca are mostly lobed or forked 

 distally, above and below. 



In the head there is a large, median lacuna which is partially 

 divided into many small spaces by strands of muscles which pass in 

 various directions through the lacuna from one side to the other. 

 Where these fibres come in contact with the blood they are clothed 

 with a layer of endothelium. Thus, instead of the two definite lacunae 

 which occur in Cerehratulus, we find the tissues of the head to be 

 permeated by an irregular series of anastomosing blood-spaces which, 

 farther back, unite into two large lacunae. These, the lateral lacunae, 

 pass backward through the cesophagal region at the sides of the pro- 

 boscis-sheath and give off branches which surround the oesophagus, 

 except on its dorsal surface. They form large, anastomosing lacunae 

 which occupy nearly all the space between the oesophagus and the 

 body-wall, so that there is very little gelatinous tissue developed. 

 The dorsal vessel, soon after its origin from the anastomosing lacunae 

 of the head, passes through the muscles of the proboscis-sheath, 

 as in Cerehratulus. In the posterior portion of the cesophagal region 

 the vessel leaves the sheath, beneath which it passes to the posterior 

 end of the body. 



The nephridial system begins a short distance back of the mouth 

 and continues nearly to the intestinal region. Near the middle of 

 the oesophagal region there is a single pair of efferent ducts from 

 which canals run both forward and backward, giving off numerous 

 branches which lie close against the walls of the oesophagal blood- 

 lacunae. 



The four-lobed brain is provided with a thin dorsal, and thick 

 ventral commissure. The side-organs are flattened and but little 

 developed. They lie just above the outer borders of the dorsal brain- 

 lobes, from the fibrous cores of which they are supplied with nerves. 

 A ciliated canal runs forward and opens into the transverse cephalic 

 slit on each side of the head. The side-organs do not come in con- 

 tact with the cephalic lacunae, but lie imbedded among the muscles 

 of the head. The lateral cords are united by a delicate nerve-plexus. 

 The dorsal nerve is but slightly developed. 



The genital products develop in sacs which alternate with the 



