466 Benjamin Sharp 



giving the results of my observations on this genus. The siphon in this 

 form is not long in proportion to the length of the animai , as we found 

 it to be with Mya^ but well developed. The mouths of the siphon are 

 beset with short conical tentacles , which are arranged in many rows. 

 At the bases of the tentacles and well protected from injury are seen 

 dark grooves, some of them being from 1 to 1,5 mm in length. These 

 are very numerous and often as many as fifty or seventy five have been 

 counted in good sized individuals. Will describes Solen as possessing 

 eyes, unless he had reference to the pigmented grooves I could nowhere 

 detect anything like an eye , especially one as complieated as he de- 

 scribes, although I have carefuUy examined the siphon both with a lens 

 and by making long series of sections of it. 



These grooves are distinctly seen with the naked eye, and as these 

 are the only places , where pigment is found , I think tbat we are safe 

 in concluding that the seat of vision , which is undoubtedly present , is 

 placed in these grooves. 



When sections are made cutting the free end of the siphon verti- 

 cally, we find that these grooves are composed of pigmented cells simi- 

 lar to those already described for other forms, and as a rule those cells 

 situated at the base or bottom of the groove are longer than those 

 placed higher up. Occasionally when a collection of these cells line 

 only one side of a groove as sometimes occurs , we find that those far- 

 thest from the edge are the longest as I have depicted in fig. 14. 



When these pigmented cells are highly magnified (fig. 9) , we find 

 the nuclei almost if not absolutely spherical ; the cells are typical cy- 

 lindrical cells. The pigment is of a brown color and most dense at the 

 free end of the cell and gradually diminishing as we approach the nu- 

 cleus, the lower parts of the cells are filled with granular protoplasm. 

 These cells do not seem to contract at the end in which the nuclei are 

 placed as seems to be the case with similar cells of Venus (fig. 5) and 

 Mya (fig. 8). Whether this is due to the fact, that Solen was more care- 

 fully prepared than the other two , or whether it is characteristic in 

 Venus and Mya I am not prepared to say. 



No nerves could be detected in Solen nor in any other form that 

 I have observed. 



As regards Solen e?ms I may say , that we have practically the 

 same state of aflfairs. I could in no way detect any difference. I also 

 had opportunity to experiment with this species and with just the same 

 result as was obtaiued for Soleti vaghia ; but as to Solen viridis^ a small 

 form , the siphons ended abruptly and there was no trace whatever of 



