No. I.] SENSE-OI^GANS OF LUMBRICUS AGRICOLA. 201 



fibres can often be traced through the basement-membrane 

 into the base of the epidermis, but it is impossible to discover 

 their further course in these preparations. That these bundles 

 of fibres are nerves can be proved by tracing them, in serial 

 sections, to the central nervous system. To avoid repetition, a 

 description of the course of these nerves will be left until the 

 silver nitrate preparation is described. 



In these preparations, the sense-organs have been found in 

 the epidermis of every region of the body except in the clitel- 

 lum, but they are most numerous in the anterior and posterior 

 metameres. In longitudinal sections, these organs are found 

 most often in the cephalic border and in the median zone of a 

 metamere. In cross sections, the most noticeable ones are 

 found in sections passing through the setae. The form of a 

 cephalic border of a metamere — curving down as it does to 

 the intersegmental groove — causes a cross section through 

 this region to pass obliquely through the epidermis. There- 

 fore the sense-organs in the cephalic border of a metamere are 

 easily overlooked in such sections. The sense-organs in the 

 metameres back of the clitellum differ from those described 

 for the anterior metameres merely in size. As the epidermis 

 is thinner in these metameres, the organs are smaller — usually 

 about 45/Lt high and i6/a wide. In a few caudal metameres, the 

 sense-organs again increase in size. 



The sense-organs not only occur in the epidermis, but Miss 

 Randolph found them among the epithelium cells lining the 

 buccal cavity. So far as I know, they have not been found in 

 this region before. The sense-organs are here found as far 

 caudad as the median zone of the fourth segment, i.e., almost 

 to the caudal limit of the buccal cavity. In this entire tract the 

 sense-organs are larger and more numerous in the dorsal than 

 in the ventral epithelium. In a given section through the 

 cephalic half of the buccal cavity, the number of sense-organs 

 in the dorsal wall varies from i8 to 31, and in the ventral wall 

 from o to 7. In the caudal half of the buccal cavity the same 

 comparative difference exists, but the organs are fewer in num- 

 ber. This difference in the relative number of orscans in the 

 two walls may be due to a difference which exists in the form 



