128 CALIFORNIA ACADEMY OF SCIENCES. 



DETAILED DESCRIPTION. 



Body-trail. The prostoraium with buccal cavity is strongly eversible, forming 

 a bladder-like apex to the body, as is so frequent in oligochneta. Somite i is very 

 narrow, especially laterally, and may readily, when viewed from the exterior, be taken 

 for part of the prostoraium. 



The body-wall contains the usual layers of which the muscular fibers show the 

 same bipinnate arrangement as in Lumbricus, etc. This arrangement is less regular 

 and pronounced in the anterior somites, but quite plain in the genital and clitellar 

 ones, especially so on the ventral side, immediately below the nerve-cord. 



Sense organs of the epidermis. All the species of Benhamia described here 

 possess a continuous row of sense organs, in the equatorial plane of each somite, be- 

 tween the set*. Outside of this equatorial circle I have not found them anywhere 

 in the epidermis; there, however, they are very plain and prominent, appearing under 

 low power and in longitudinal sections, as a large pellucid spot in the center of each 

 somite. The organ consists of two distinct kinds of cells, a double line of large lunate 

 cells, surrounding a row of sense cells, several layers thick. These lunate cells are 

 generally three or more thick in the row, evidently modifications of the common 

 goblet cells of the epidermis. They do not stain with the ordinary aniline colors, or 

 only so with difficulty, and generally remain transparent and white. These lunate 

 cells run continuously around the somite, and enclose between them bunches of sense 

 cells, which may now and then be seen to penetrate the cuticle (fig. 20). Somewhat 

 similar sense organs have been known in Lumbricus, etc., for considerable time, but 

 have lately been described more in detail by Richard Hesse and F. E. Langdon. 

 The sense organs of Benhamia difier from those of Lumbricus agricola (pi'obably a 

 collective name used for some East American AUolobophora) in two prominent 

 points. Presence of the large lunate cells in Benhamia, which are not seen in 

 Lumbricus. The continuous and broad circle of these organs in Benhamia, while in 

 Lumbricus they appear to be much further apart. Unfortunately my Benhamias 

 were collected at a time when no special preparation for nerve structure was feasible, 

 and this made it impossible to work out the details as minutely as desirable. The 

 work had alread}^ been finished when Langdon's beautiful paper reached me. 

 Fig. 20 represents a section of the body-wall in somite iv. Letters org. signify 

 the sense organ. 



Besides these epidermal sense organs I find in all the Benhamias, observed by 

 me, a large zone in the buccal cavity characterized by almost cubical transparent 

 cells arranged in one single row deep, just as the epithelial cells in the pharynx, but of 

 the same nature as the transparent cells in the sense organs of the epidermis. This zone 

 is nearly always folded against itself like a sac, and is of considerable extent, as long 

 or longer even than the pharynx. In certain places apparently scattered about, but 

 principally near the opening of this sac, I find clusters of sense cells of the same 

 structure as those of the epidermis. They are all narrow, do not reach below 

 in the coelomic cavity, but end in this direction in line with the pellucid cells and 

 connect at the end with nerve fibres. The free ends penetrate above in what ap- 



