412 



They begin by describing three sets of experiments in the way of 

 injections, to show that water can find its way into the pericardial 

 blood-lacunae through the organ of Bojanus ; and from thence into 

 the vessels which carry the systemic blood towards, and only into 

 those which carry it towards, the gills. 



The results of two other sets of experiments are next adduced in 

 proof of the non-existence in the blood-vascular system, first, of 

 any lacuna save in this pericardial space ; and, secondly, of any com- 

 munication with the exterior by pores, save such as the two sacs of 

 the organ of Bojauus may be held to represent upon a gigantic scale. 



What is new, however, in this part of the paper, is not so much 

 the conclusions as the methods the authors have adopted for demon- 

 strating them. 



In proceeding to argue for the existence of a system of tubes 

 distinct from the blood-vascular system, the authors begin by con- 

 trasting the appearance which the non-generative part of the foot 

 presents when it is injected, as it is easily, from the orifice which 

 serves as generative outlet, with that which it presents when injected 

 from the blood-vessels. 



Secondly, they show that it is possible when the blood-vessels are 

 already fully occupied by an injection of one colour to cause a second, 

 or when the artery and the vein have been filled with differently 

 coloured fluids, a third system of vessels to make their appearance 

 throughout the foot-mass by throwing a differently coloured injection 

 into the oviducal outlet. 



Thirdly, microscopic examination of animals thus treated excludes 

 the idea that the fluid thus interposed between and amongst blood- 

 vessels has found its way simply into interstitial spaces left between 

 them and the tissues, as it shows that it is contained within a system 

 of tubes as well defined and limited off from the surrounding tissues, 

 as is the fluid which has been thrown into the blood-vessels them- 

 selves. 



That the water which has been shown to enter the body by the 

 intermediation of the organ of Bojanus finds its exit by the same 

 route, the authors believe to be rendered in the highest degree im- 

 probable, by the fact that they have found it impossible to make 

 fluid pass in the direction this hypothesis postulates ; that is, from 

 the blood-vessels, into the pericardium. 



