STRUCTURE OP THE NBPHRTDIA OF DINOPHILUS. 517 



On the Structure of the Nephridia of Dinophilus. 



By 



Cress well Shearer, 



Trinity College, Cambridge. 



With Plates 29 and 30. 



21^ Schmidt (22) was the first to draw attention to the 

 nephridia of Dinophilus iu 1848, which he simply men- 

 tions in D. vorticoides as two longitudinal vessels. They 

 seem to have escaped further attention till Korschelt (11) in 

 1882 again mentioned their presence in D. apatris. It is 

 to Harmer (8), however, that we owe the most complete 

 description of the nephridia. In 1889 he described five 

 pairs in D. tteniatus, a species found abundantly in the 

 tidal pools of Plymouth Bay. Since then they have been 

 studied by Schirakewitsch (23) in D. vorticoides from the 

 White Sea. This last author investigated them by means of 

 the intra vitam method of staining with methylene blue, 

 but was able to add little to Harmer's account of their struc- 

 ture. 



I have long suspected from both Harmer's and Schimke- 

 witsch's descriptions that the nephridia of Dinophilus 

 would finally prove to be closed internally by flame-cells 

 similar to those Goodrich (5) has described under the name 

 of solenocytes, in certain Polychfets, Amphioxus, and 

 the Actinotrocha larva of Phoronis. Only during the 

 present season, hoAvever, have I been able to verify this, and 

 to definitely determine that they are furnished with typical 



- solenocytes. 



This is, I think, a point of some morphological interest. 



VOL. 50, PART 4. NEW SERIES. 38 



