PACIFIC COAST OLIGOCH^TA. 163 



ments in the clitellum which stain deeply with hferaatoxylin. These cells offer 

 nothing characteristic of the species. They are the last to be affected by tropoeolum 

 and orange, their mucin remaining intensely blue. Their nuclei are compressed and 

 placed in the posterior part of the cell in the triangular mass and extremity, staining 

 black in the iron-lack (fig. 103, 2). 



3. Short club cells. These are of very uniform size, their free ends forming a 

 marked line all around the clitellum interior to the goblet cells. The free end of 

 this cell is club-shaped and generally regular in outline. The heights of the indivi- 

 dual cells are quite even, and, as these cells stain darker than the following kind, 

 they form a marked contrast to all others. The granulation is coarse and regular, but 

 does not stain readily with hsematoxyliu. It takes, however, deeply the red aniline 

 stains. On the dorsal side of the clitellum these cells reach inward about J of the 

 whole width of the epithelium, while on the ventral side, they constitute the only 

 so-called clitellar cells. The nuclei of these cells are oval and always prominent 

 (fig. 103, 3). 



4. The pre-eminently clitellar cells consist of several, 3 or 4, different lengths. 

 This class of cells are in many genera, such as Lumbricus, etc., massed in columns, 

 often very regular, and separated by septa. In Sparganophilus these cells are not 

 arranged in columns, but distributed almost regularly all through the epidermis, of 

 which they occupy about § of the whole mass. At certain intervals, however, may 

 be seen a. thin triangular septa of connective tissue with nuclei, projecting down- 

 wards or outwards from the muscular layers, dividing this part of the epidermis in 

 numerous irregular pyramidal masses, which latter are homologous with the columns 

 in Lumbricus, etc. The nuclei of these clitellar cells are shrivelled up and situated far 

 back in the triangular apex where the cellular plasma is especially agglomerated. 

 There is no such granular secretion in this class as in the former, and they stain much 

 less intensely than No. 3. These cells occur only dorsally to the tubercula pubertatis, 

 and are entirely absent from the ventral side between the tubercula pubertatis. 



5. Here and there we find intermediate varieties of oval and club-shaped 

 cells longer and wider than the epidermal supporting cells and furnished with large 

 round nuclei. 



6. Connective tissue cells with large round nuclei, especially prominent 

 between the circular muscular layer and the tall clitellar cells. At intervals this 

 tissue forms triangular projections outwards, separating bunches of cells four or five 

 wide and of different sizes. This tissue is generally accompanied by numerous 

 capillaries. 



Tubercula 2^ubertati?.. These organs are very prominent, and situated on a 

 nearly continuous ridge occupying somites xviii-xxii. Benham has described this 

 structure in detail in his species Sp. ta-niesis, and called attention to the fact that it is 

 composed of long narrow cells, which are modified clitellar cells. In Sparganophilus 

 Benhami these cells are of two kinds, as far as regards the form. 



a Some which are very narrow, longer than the others, and narrowest at the 

 free end. All of this class are grouped in such a way that they radiate outwards 



Memoirs, Vol. II, 5. January 7, 1896. 



