and Oviducal System in the Lamellibranchiate Mollusks. 449 



tural life : our injections were always performed under water, by 

 which and by other means as much support was given to the 

 animal's body and its several parts as the water and the shell 

 gave to it during life. Means were always adopted for securing 

 that the animal died with its muscular system in a state of re- 

 laxation. We found the prussian blue injecting-fluid of Prof. 

 Beale's * invention to possess many properties especially recom- 

 mending it for use in our experiments, but we employed several 

 other fluids as well. 



Experiment 1. — If an Anodon or Unio (size is of little conse- 

 quence in this experiment, though large size is a convenience in 

 most) be removed from its shell without injuring the some- 

 what easily injured tissues which limit the secretingvstructui'e 

 of the organ of Bojanus, and supported in water with its foot 

 downwards in such a manner as to put its pericardial lacuna, 

 and the parts in connexion with it, as nearly as possible into the 

 condition in which they may be supposed to be in in the shell 

 during life, and if an injection be then made into the pericardial 

 lacuna, the following results will be seen to take place. The so- 

 called "reddish-brown organ of Keber" (a plexus of vessels 

 rich in pigmentary deposit, continuous with other vessels not 

 so coloured in the mantle and elsewhere, and bounding the 

 pericardium on either side, and opening into it by several patent 

 orifices at its anterior end) will become filled with the injecting- 

 fluid first ; next the gill-vessels, and sometimes together with 

 them, yet not invariably, the systemic veins; and lastly the 

 external orifice of the organ of Bojanus will, on removing the 

 animal from its prone position, be seen pouring out the injec- 

 tion on either side of the animal's foot. 



Experiment 2. — A large Anodon was injected with a red 

 stiffening-injection from the central branchial vein, a vessel 

 readily injectible, lying as it does in the gill-cavity superiorly 

 between the two innermost lamina? of the gills, in the angle 

 where they become continuous with each other posteriorly to 

 the posterior edge of the foot, with the following results : — The 

 auricle and ventricle were filled to distention, the reddish- brown 

 organ as well, and, besides the reddish-brown organ, the rest of 

 the mantle, up to within a quarter of inch of its free edge. No 

 fluid, however, had penetrated into the pericardial space. The 

 absence of penetration into the pericardium we have invariably 

 had to record in our numerous injections from the branchial 

 veins, even when the injection is noted as having been so en- 

 tirely successful as to have passed through the aorta in such 

 abundance as to inject in fine ramuscular divisions the edge of 

 the muscular foot. 



* ' How to work with the Microscope/ p. 78, 185/. 



Ann. $ Mag. N. Hist. Ser.3. Vol.x. 30 



