452 Dr. G. Rolleston and Mr. C. Robertson on the Aquiferous 



reasons for demurring to these views, in which we ourselves at 

 one time participated. It will be necessary to give the details 

 of two sets of experiments, to show how we came to give up an 

 opinion which can plead such high authorities as those we have 

 cited for its defence. 



Experiment 4. — A large Anodon, having died with its foot in 

 a semidistended state, was injected from the venous sinus which 

 receives the blood from the systemic veins and distributes it to 

 the renal-portal system, with the prussian-blue injection already 

 spoken of. The injection spread over the liver and over the 

 whole of the generative gland, and the exclusively muscular part 

 of the foot, spreading itself in especial richness along the free 

 edge. No pressure which we subjected the foot to, when thus 

 fully injected, caused any of the blue injection, easily and readily 

 though it runs, to issue forth. Subsequently to this, a stiffening 

 injection of red colour was thrown into the foot-mass from the 

 oviducal outlets. This second injection spread itself very richly 

 over the ovary, over the liver, and into the muscular foot, along 

 the free edge of which it issued in small jets without any pressure 

 being applied. 



We will disregard, for the moment, the bearing which this 

 experiment has upon the distinctness from the blood-vascular 

 system of the system of tubes in the muscular foot, to which the 

 stem opening (under the name of oviduct) into the mantle-cavity 

 leads, and we will relate the details of another set of experiments, 

 which led us to consider the phenomenon of the jets issuing 

 from the foot-edge as due, in spite of the frequency Math which 

 we have seen it recur, to violence done, possibly unavoidably, 

 to the delicate limitary tissues of these aquiferous tubes. 



Experiment 5. — A Unio margaritifera, which had died with 

 its foot quite relaxed, had the blue injecting-fluid introduced 

 into its aorta, its venous system, and through the oviducal ori- 

 fices, until the foot, from a state of perfect softness, became 

 tense and swollen up. On presswe, none of this triply -injected 

 blue fluid could be made to issue forth from the foot-edge ; but 

 small hernia-like projections of transparent membrane rose out like 

 bubbles all along the foot-edge. They contained at first a trans- 

 parent fluid, but after a little pressure they became filled with 

 the blue injection. The thinness and transparency of these little 

 sacs will account for the rarity of their appearance, and the 

 comparative frequency with which jets of injected fluid have 

 made themselves noticed in the region corresponding to the 

 csecal endings of tubes which these sacs must be held to repre- 

 sent. The depressions and pores which do exist in the foot of 

 the Lamellibranchiate mollusk we believe to be glandular in 

 character,, and destitute of any direct communication with the 



