128 CALIFORNIA ACADEMY OF SCIENCES. 



DETAILED DESCRIPTION. 



Bndy-yall. The |)ro.stoinium with buccal cavity i.s strongly ever.sible, foiinir)g 

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

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

 for part of the prostomium. 



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. 



Sensa 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 setiB. Outside of this equatorial circle I have not found thom anywhere 

 in the epidermis; there, however, tliey are very plain ami prominent, appearing under 

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

 somite. Tlu' 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 difl'er from those of Lunihricu^ agricdla (probably a 

 collective name used for some Ea.st 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 a[)art. Unfortunately my Benhamias 

 were collected at a time when no special preparation for nerve structure was feasii)le, 

 and this made it impossible to work out the details as minutely as (lcsirai)le. The 

 work had already been linislicd 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, ubservetl 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. Tiiis zone 

 is nearly always folded against itself like a sac, and is of considoral)lo extent, as long 

 or longer even than the pharynx. In certain j)laces apparently scattered about, but 

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

 structure as tho.se of the e|)idermis. They are all narrow, do imt reach below 

 in the co'lomic cavity, but end in this direction in line with the pellucitl cells and 

 connect at the end with nerve fibres. Tiie free ends penetrate above in what ;ip- 



