633 



of the contents of a single bobbin or 137 yards. A glance from left 

 to right on the same horizontal line shows the comparative value of 

 each combination in the several experiments. One or two small 

 irregularities in Table II. in the six-cell results, are doubtless due to 

 the poles of the magnet not having been ground true. 



With respect to durability, the graphite plates in use since 1850 

 are in as good condition as the new ones now in course of manu- 

 facture. Silver plates employed by us under like circumstances, 

 commenced perishing after twelve months or more of use ; they 

 crumble away in great measure, they cut apart at the surface level, 

 and they get eaten into holes throughout. 



II. " On the Aquiferous and Oviductal Systems in the Lamelli- 

 branchiate Mollusks." By GEORGE ROLLESTON, M.D., 

 Lee's Reader in Anatomy, and CHARLES ROBERTSON, Esq., 

 Curator of the Museum, Christ Church, Oxford. Com- 

 municated by Dr. ACLAND. Received January 6, 1859. 



(Abstract.) 



In this paper the authors bring forward two views as to the ana- 

 tomy of the Lamellibranchiata. 



1 . The first part of the communication is devoted to an examina- 

 tion of the commonly -received opinion as to the outlet of the ovarian 

 system, and arguments are brought forward to show that the orifices 

 usually supposed to discharge this office are in reality the exhalant 

 orifices of a water-vascular system. The positive arguments drawn 

 from the way in which fine injections thrown in by these orifices 

 distribute themselves throughout the visceral mass, and from the 

 relative position of orifices acknowledged to belong to a water- vascu- 

 lar system in other mollusks, are confirmed by a consideration of 

 the improbability attaching to the old view, which regarded as ovi- 

 ducts in mollusca two canals, which lying one on either side of the 

 body, yet communicate freely with each other at no great distance 

 from their termination, and which lie far away from the lower seg- 

 ment of the intestinal tube. The inhalant aquiferous orifices are 

 considered to be indicated by a belt of parasitic animals impacted 

 in the foot tissue, as represented in one of the figures. 



