94 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D. Ser. 



a great similarity between the structure of these tubercles 

 in the present species and those found in S^arganophilus. 

 The glandular cells (fig. 20) are long and narrow, pear- 

 shaped, or oblong and club-like, with round nuclei near the 

 wide distal apex. Between them are also found other 

 glandular clitellar cells, as well as a few hair-tipped sense- 

 cells. The most interesting feature of these true tubercula 

 pubertatis cells is that they extend through the two muscu- 

 lar layers of the body-wall to the coelomic epithelium, but 

 do not penetrate into the coelomic cavity (fig. 19). Similar 

 cells are found in Diplocardia Koebelei. 



Beddard has shown that there are, as regards structure, 

 two kinds of tubercula pubertatis. In one of these the 

 glandular cells extend into the coelom, as in Perichceta, 

 while the other kind is associated with glands which do not 

 extend into the coelomic cavity, but which are confined to 

 the epidermis. Beddard's suggestion that this morpholog- 

 ical distinction may not prove to be of very great importance 

 is undoubtedly correct. In Pontoscolex we find that these 

 glands are intermediate between the two extreme types. 

 In a very few instances I have observed one or two of 

 them penetrating the coelomic epithelium, which makes 

 the transition all the more complete, and proves what 

 has already been suggested (Eisen 18), that in the ter- 

 restrial Oligochseta the tubercula pubertatis are always of 

 the same morphological nature, whether their exterior forms 

 take the shape of ridges or papillae; also that the differences 

 consist principally in the size of the glands and in the num- 

 ber of sense-cells between them. In Pontoscolex these 

 sense-cells are few and small; they are never found on the 

 ridge of the papillae, but are confined to a narrow groove on 

 either side, very much as in Sparganophtlus. The tips of 

 the sense-cells project through the cuticle; they are knob- 

 like, appearing very much like minute pin-heads, and are 

 about as long as the cuticle is deep (fig. 20) . 



The tubercula pubertatis glands do not immediately join 

 the clitellar glands. There is a narrow zone of narrow 

 glandular cells which separates the tubercula pubertatis 

 ridge from the regular clitellar cells (fig. 20). 



