148 Royal Society. 



March 18. — A paper was read, entitled, "On the Blood-proper 

 and Chj'lo- aqueous Fluid of Invertebrate Animals." By Thomas 

 Williams, M.D. 



In this paper the author has accumulated numerous observations, 

 founded upon dissection and microscopic inquiry, to prove that there 

 exist in invertebrate animals two distinct kinds of nutrient fluids ; 

 that in some classes of this sub-kingdom these two fluids coexist in 

 the same organism, though contained in distinct systems of con- 

 duits, while in others they become united into one. The author 

 proposes to distinguish these two orders of fluids under the denomi- 

 nations of the blood-proper and chylo-aqueous fluid. The former is 

 always contained in definitively organized (walled) blood-vessels, 

 and having a determinate circulatory movement; the latter, with equal 

 constancy, in chambers and irregular cavities and cells, communicating 

 invariably with the peritoneal space, having not a determinate cir- 

 culation, but a to-and-fro movement, maintained by muscular and 

 ciliary agency. He then adduces evidence, derived from dissection, 

 in proof of the statement that the system of the blood-proper does 

 not exist under any form, the most rudimentary, below the Echino- 

 dermata ; that, in other words, the system of the true blood, or of 

 the blood-proper, begins at the Echinodermata. The author then 

 shows that below the Echinodermata, namely in the families of Polypes 

 and Acalephse, the digestive and circulatory systems are identified, 

 and that consequently the external medium is admitted directly into 

 the nutrient fluids. He considers that this circumstance constitutes 

 a fundamental distinction between the chylo-aqueous system and 

 that of the blood-proper, into which, under no conditions, is the ex- 

 ternal inorganic element directly introduced. 



He conceives that his observations suffice to establish the law, 

 with reference to the chylo-aqueous fluid, that in every class in 

 which it exists, it is charged more or less abundantly with organized 

 corpuscles. This is an invariable fact in the history of this fluid. 

 His inquiries show that these corpuscles are marked by distinctive 

 microscopic characters, not in difl^erent classes and genera only, but 

 in diff'erent species, entitling these bodies to great consideration in 

 the establishment of species. 



The paper then proceeds to demonstrate the proposition, that in 

 those classes, as in the Echinodermata, Entozoa and Annelida, in 

 which, in the adult animal, these two orders of fluids coexist, though 

 distinct, in the same individual, there prevails between them, as 

 respects their magnitude or development, an inverse proportion ; that 

 while, as instanced in the Ecliinoderms, the chylo-aqueous fluid 

 filling the ciliated space between the stomach and integument is 

 considerable in volume, the blood-proper and its system are little 

 evolved ; that while, as in the Entozoa, the chylo-aqueous fluid is 

 still the most important fluid element in the organism, the blood 

 system is proportionally rudimentary ; that in the Annelida, espe- 

 cially the higher species of that class, the chylo-aqueous fluid almost 

 disappears, while the system of the true blood acquires, illustrating 

 the law of inverse proportion, a correspondingly-augmented develop- 



