coe: nemerteans of west and northwest coasts. 11 



and constitutes a more or less definite cutis. In certain forms 

 (Taeniosoma and a few of the Lineidae) the cutis consists of a 

 very massive framework of connective tissue supporting an abun- 

 dance of compound glands, while in most other heteronenierteans 

 the connective tissue is partly replaced by longitudinal muscles. 



In Taeniosoma the cutis usually presents two distinct layers, of 

 which the outer is closely packed with compound or clustered 

 glands, doubtless homologous with those of the integument of the 

 Paleonemertea. These cutis glands have a great affinity for haema- 

 toxylin stains, and each gland consists of a group of 6 to 20 or 

 more pear-shaped gland cells, all of which pour their secretions into 

 usually a single duct which passes to the surface of the integument. 

 The inner layer is made up of a thick mass of connective tissue, 

 commonly composed of coarse fibers, but sometimes giving place to 

 delicate fibrils imbedded in a gelatinous matrix. 



In most species of the Lineidae, the connective tissue to a great 

 extent gives place to longitudinal muscular fibers, which surround 

 the compound glands and which lie immediately outside the longi- 

 tudinal muscles of the body walls. In many of the Lineidae the 

 longitudinal muscles of the cutis are often so intimately connected 

 with those of the body Avails that any sharp line of demarcation 

 between cutis and body musculature is impossible, and, indeed, in 

 many cases the cutis glands sink completely beneath the longi- 

 tudinal muscular layer of the body wall to lie against the nervous 

 plexus immediately external to the circular muscular layer. Two 

 distinct varieties of glands, of which one is simple and the 'other 

 compound, often occur in the cutis of the same species. 



The thickness of the cutis often equals that of the integument, 

 and may in some instances become several times as great. As a rule, 

 the thickness is much greater in Taeniosoma than in the Lineidae, 

 and is greater in the anterior than in the middle and posterior por- 

 tions of the body. In Zygedpolia and numerous other forms of 

 the Lineidae, any distinction between the cutis and the outer longi- 

 tudinal muscles of the body wall would be merely artificial. 



Between the integument and the cutis in most nemerteans a 

 double set of subepithelial or integumental muscles is^ developed. 

 These consist of a very thin outer layer of circular fibers, and a 

 somewhat thicker, but yet delicate, layer of longitudinal muscles. 



