[)(issil)le that caii^ful liistdluti'iral work mav demonstraio 

 tlip j)r('s(>ii((' of ciliated cells modified to form sense colls 

 somewhat resembling- tlH> rods of the vertebrate eye. 



The basement membiane is structureless, and is com- 

 })osed of the intercelhilar substance around connective 

 tissue cells. It takes a deep stain with hiPmatoxylin or 

 nig-rosin. though it is ajjiiarently unaffected by the carmine 

 dyes. Beneath the basement membrane is found a thin 

 layer of fine circular muscle fibrils, and underneath those 

 again a ditfuse layer of small gdands, each composed of 

 scxeral c(dls. The secretion of these cutis g-fands stains 

 deeply with carmine or lueniatoxylin, and by it the minute 

 ducts of the g'lands may l)e traced to their external oj^en- 

 ing's. ^lixed up with the cutis gdands are numbers of 

 connective tissue cells of a peculiar form containing pig- 

 ment. These will be referred to later among the connec- 

 tive tissues. Around the cutis glands are also found the 

 most external fibres of the external longitudinal muscle 

 layer. The fibres are separated into a numl)er of small 

 bundles by the connective tissue, a structureless invest- 

 ment exhibiting the same staining alftnities as the base- 

 ment membrane, with which it is piobably identical as 

 regards composition. 



Separating the outer longitudinal and the circular 

 muscde layers (PI. IL, hgs. 1 and 'J. PI. III., fig. 8) 

 is a tunic of nervous tissue, consisting of fibrils o-iyen 

 off from the lateral nerve cords, wlii(di also lie between 

 the same two muscle layers. The ciicular muscle layer is on 

 the whole not so thick as the outer longitudinal layer, and 

 of about the same thickness as the inner longitudinal 

 layer which it immediately invests. Towards the posterior 

 portion of the body the outer longitudinal muscle layer 

 becomes greatly diminished, whilst the internal longi- 

 tudinal layer here surpasses the circular layer in thickness. 



