138 



Professor Kolliker maintains the fungoid nature of these 

 tubuli in shells as well as in other hard tissues of animals, 

 as fish scales, &c. 



Wedl, another investigator, considers the tubuli in all bi- 

 valves as produced by vegetable parasites, and that no other 

 interpretation can be given. 



This view does not seem to be borne out by the section 

 of another shell which was exhibited, " Area navicula,'' in 

 which the tubuli are always present, forming an integrant 

 part ; they are disposed in a straight and tolerably regular 

 manner between the ridges of the shell; moreover, they 

 have neither the irregularly branched structure nor the 

 sporangia. 



Erratum. — In the last number of the ''Proceedings," 

 p. 99, line 9 from top for '' Regnalt" read Renault. 



