2S0 ANDREWS. [Vol. V. 



there are but six or seven spots upon a branchia, each a collec- 

 tion of about as many pigment cells. 



Macerations show only simple pigment cells, much like the 

 small pigment cells of the eye of Potamilla. Surface views also 

 fail to indicate any refracting bodies whatever. 



In sections the spots occur here and there, and are often only 

 one or a few cells with pigment granules in them, and nothing 

 else to distinguish them from the ordinary epithelium' over the 

 branchia. In some cases, as seen in the transverse section, 

 Fig. 15, the pigmented cells are club-shaped, larger at the outer 

 ends, and hence crowded into a triangular arc in the section. 

 The outer, swollen ends may also contain less pigment, appear- 

 ing vacuolated and somewhat clear, but showing no trace of any 

 special refracting body. 



It will be noticed that the epithelial cells are much elongated 

 and are slender, with the nucleus near the base, where the cell 

 is in contact with the heavy basement membrane ; occasionally 

 a nucleus appears high up near the outer end of the cells, appar- 

 ently in a filamentous cell body, this occurring both in pig- 

 mented areas and in non-pigmented areas of the epithelium. 

 Now when the spot is depigmented, as in Potamilla, only these 

 elongated cylindrical cells and their nuclei are seen, no inclu- 

 sions, nor refractive bodies, nor even cuticle, for the cells seem 

 to have an exceeding delicate cuticle, if any at all. 



In some tangential sections, however, certain larger, clear cells 

 are seen, many times wider than the common epithelial cells, 

 and irregularly scattered amongst them, as in Fig. 16. 



These clear areas appear to be merely non-pigmented, watery, 

 or vacuole-like parts of the protoplasm in the swollen, outer ends 

 of a few cells, and certainly have no such appearance as the 

 refractive parts in Potamilla. 



The " eye spots " of this Annelid are thus scarcely compara- 

 ble to those of Potamilla, but. are to be regarded as mere areas 

 of pigmented, epithelial cells, in which a few may be somewhat 

 clearer at the outer end. 



The case stands quite differently with a large Sabella very 

 common along the shores of GreenTurtle Cay, Bahamas. 



This fine species is undoubtedly S. mclanostigma, of Schmarda 

 (14), as more fully described by Ehlers (8), supposing that both 

 had only small, immature specimens. However, I find two rows 



