KUTCHIN. — PERIPHERAL NERVOUS SYSTEM OF AMPHIOXUS. 609 



out into the cutis and end in tufts. Fusari ('89) says that the cutane- 

 ous nerves divide into fine branches immediately beneath the cuticula 

 (the hmiting membrane of Langerhans), and that anastomoses are 

 frequent in the skin of the ventral region, but rare on the sides and 

 dorsum. The branches in the ventral region pass into fine free-ending 

 fibrillae, or before ending show a spindle-shaped, nucleated enlarge- 

 ment. In all other regions (with the exception of the mouth) nerves, 

 penetrating the cuticula, appear to terminate after a short course in 

 free endings, though they can be traced to the bases of epithelial cells. 

 Fusari is uncertain, however, whether there is any connection between 

 these nerve fibers and the cells. He saw the sensory cells of Langer- 

 hans, and though inclined to his views, contends that a connection 

 with the nerves is not demonstrated. He believes that the description 

 of the nerve-net given by Marcusen is based on a peritoneal rather 

 than a dermal plexus. He\Tnans et van der Stricht ('98, p. 33) regard 

 the so-called sense-cells of Langerhans as merely compressed and 

 flattened "cyclinder" cells, l^earing no special relation to the nerves. 

 These authors saw branches of a dorsal ner^•e form among themselves 

 a plexus on the border of the fins; but they never found the plexuses 

 mentioned by Fusari as frequent in the ventral region. According 

 to these writers the nerve fibers ramify under the cutaneous epithelium, 

 and terminate between, and perhaps within, ordinary epithelial cells. 

 They found no special sense-organs in the skin, in connection with 

 nerve fibers. 



Retzius ('98) is convinced that cutaneous fibers end free at the 

 bases of epidermal cells. He saM' two kinds of cells in the epithelium, 

 one smaller than the other, but neither bore a thread- or spine-like 

 process. He found no direct connection between these cells and nerve 

 fibers, nor could he discover any true peripheral sense-cells connected 

 with nerves. Dogiel (:02) states that the "Xervi cutanei dorsales 

 (laterales et ventrales) " are pure sensory branches without any motor 

 fibers. These gradually divide in their course to the superficial layers 

 of the skin, continually giving off branches of various lengths and 

 thicknesses, which anastomose with similar neighboring branchlets 

 to form a more or less elaborate plexus, his "Grundgeflecht." This 

 plexus is especially plain, he says, in the skin of the ventral region. 

 His further description is as follows: The branches from this plexus 

 ultimately reach the homogeneous layer of the skin immediately 

 beneath the epithelium, and can be observed in good preparations to 

 pass through small canals in this layer. Each then divides into three 

 or four or more fine l^ranchlets, which spread out radially. These 



