70 



B ALANOGLOSSID A . 



first sight the view that the epidermis is many -layered. These 

 long cells, into which the epidermis breaks up when teased or 

 otherwise ill-treated, are connected together by numerous 

 lateral processes (Fig. 57), and are prolonged internally into 

 fine fibres which enter the nervous felt-work found in the 

 deeper part of the epidermis over the greater part of the body. 

 The thickness of .the epidermis and the number and disposition 

 of the gland cells varies in different places. The muscles and 

 connective tissue are entirely derived from the walls of the 



coelomic sacs and 

 will be considered 

 in connexion 

 with those struc- 

 tures. 



The nervous 

 system. In the 

 lower stratum of 

 the ectoderm just 

 external to the 

 basement mem- 

 brane there is the 

 feltwork of fine 

 fibres almost en- 

 tirely without 

 nuclei, which has 

 just been men- 



This tis- 

 |g SUPPOSed to 

 nerVOUS in 



function and 

 strongly recalls the corresponding layer found in many 

 Nemertini. It is thickened along the dorsal middle line of the 

 collar and trunk and along the ventral middle line of the trunk. 

 These constitute the dorsal and ventral nerve cords (the collar 

 portion of the dorsal cord is invaginated, see below). They are 

 connected at the junction of the collar and trunk by lateral 

 commissures which like them are special concentrations of the 

 nerve plexus and lie in the ectoderm at the base of the collar 

 or atrial groove. The dorsal nerve cord extends forwards on to 

 the base of the proboscis to become continuous with the general 



Fia. 57. Preparations of the epidermis of the collar of Balano- floned 

 glossus clavigerus (after Bateson). A, a similar preparation 

 more highly magnified, showing the long spindle-shaped cells g\j 

 passing internally into fine fibres ; B, portion of epidermis 

 teased and pressed out, showing elongated cells united at their fog 

 outer ends by numerous connections. 



