Aquiferous and Oviducal S?/sfem in Lamellihranchiata. 427 



stem of tubes forming an aquiferous tree, the trunk of which serves 

 as an outlet for the generative products, whilst many of its 

 branches spread throughout the foot into regions not occupied by 

 the organs of reproduction. This system is such a one as the peri- 

 Tisceral chamber has been shown to be by Mr. Hancock in the 

 ' Philosophical Transactions ' for the year 1 858, spreading itself into 

 ramifications, some of which are, whilst others are not, in connexion 

 with the reproductive glands. The authors allow, and indeed 

 show in the way of experiment, that it is possible for the water in 

 which the animal lives, to become intermingled with the blood within 

 its vessels by the route of the organ of Bojanus, and it will be seen 

 from what has even already been said, that they suppose the aqui- 

 ferous system to be fed with water by transudation of that fluid 

 irom the blood-vessels. 



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-lacunse 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 Bojanus 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 veiu have been filled with diflferently 

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

 throughout the foot-mass by throwing a diflferently 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 bv 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 makg 



