Langdon, Sense-organs of Nereis virens. 6'j 



at the same rate as the cuticular layer grows by addition to its 

 inner surface, or else the strands must shift their attachment. 

 The former appears the more probable at present but it can only 

 be decided by further study. 



The basal processes from these anchoring cells are never 

 beaded or varicose as are the central processes from the nerve- 

 cells. Over the surface of each one can always perceive either 

 a single row or two parallel rows of small blue cylinders like 

 those of the peripheral processes only slightly larger. This ap- 

 pearance I have never seen in a nerve-fiber of Nereis virens but 

 have often found on the surface of a muscle-fiber. The fact 

 that these broken cylinders, instead of the varicosities usual in 

 nerve tissue, are found in the central processes which are free 

 from other structures except at their ends, shows that their 

 form can not be due to the processes being firmly embedded in 

 a surrounding tissue, as one might suppose from a study simply 

 of the peripheral processes, but must be due to some intrinsic 

 difference in the tissues themselves. These basal processes can 

 be traced directly past the nerves in the base of the epidermis 

 to tJie pcnpheral end of one of the muscles zuhieh pass vi large 

 large 7mmbers to the epidermis. Sometimes these processes ap- 

 pear to enter the muscle itself and sometimes to pass onto its 

 outer surface. It would, therefore, appear that tJiese anchoring 

 cells serve for the attachment of muscles to the cuticula. The per- 

 ipheral strands embedded in the cuticula anchor the cells at' 

 their peripheral ends ; the basal processes are either interwoven 

 with the connective tissue at the peripheral end of the muscle 

 or else actually form this tissue itself, thus forming a sort of 

 muscle tendon. 



It will be remembered that a number of rather large pores 

 were found in the cuticula around the perforated membranes 

 belonging to the diffuse sense-organs in the tentacles and the 

 tips of the palps. (See Plate I, Fig. 8). In the palps many 

 small muscles pass toward the cuticula among the bodies 

 of the epidermal cells. It seems to me probable that these 

 muscles are attached to the cuticula by just such anchoring 

 cells as are described above and that this attachment is strong 



