170 REPORT — 1851. 



The coagulating principle consists of fibrine, and there can be no doubt 

 that thp great bulk of the fluid portion is composed of sea-water. The mor- 

 photic elements vary in a remarkable manner in different species ; that is, 

 for the same species the corpuscles of the peritoneal fluid are constant, 

 and nearly the same for every season of the year. In different species, there- 

 fore, these solid elements become signs of specific distinction, but the specific 

 variation is much less marked than the generic ; this is exemplified in the 

 instances of the Spios and Terebellce. In Sjjio coniocephala these corpuscles 

 are large flattened oval cells, enclosing smaller elliptical bodies and a nucleus, 

 and presenting a singularly serrated border. (Plate II. fig. 1.) In Spio vul- 

 garis, a smaller species of the same genus, the same bodies occur under a re- 

 duced size ; the serrated edges, however, are still observed. The serrations 

 are not endowed with any motive property, for these cells manifest no loco- 

 motive power. The otm of these same Annelids are orbicular, nucleated 

 bodies, and differing strikingly from the serrated corpuscles just described ; 

 these latter are always present in the peritoneal fluid ; the ova are very 

 seldom to be found. These facts, which are readily and demonstratively esta- 

 blished, prove beyond doubt that the serrated bodies are not germ-cells. 

 The illustrations present them in the maturity of growth ; they never attain 

 a larger size. In two species of Terebella which abound on these coasts, the 

 peritoneal fluid contains morphic elements of a similar character, and no less 

 specifically peculiar. 



These bodies, in Terebella nebulosa, the larger of the two species, are 

 smooth-edged oval cells, slightly compressed, containing six or seven or more 

 oil-globules, highly refractive, and filled with spherical molecules, floating 

 in a fluid possessing a refractive power greater than that of the outer fluid 

 (Plate If. fig. 2). In these bodies no nucleus is discoverable, a fact which 

 clearly distinguishes them from true ova. 



They are commonly however mistaken for ova in this species, and the 

 peritoneal chamber is accordingly described as a marsupium or incubating 

 cavitj' ; additional proofs will be afterwards adduced of the fallacy of this 

 conclusion. In this species, other bodies than those described floating in 

 the peritoneal fluid may be seen ; these latter consist of spindle-shaped 

 and irregular cells, fragments of cell-membrane and other compound bodies, 

 all differing from the regularly oval cells which constitute the bulk of the 

 solid elements of the fluid. The spindle-figured bodies, especially when affix- 

 ing themselves at one extremity into a stellar bunch, may be readily mistaken 

 for sperm-cells, with which, however, on other grounds, they are not to be 



vidus." From tliis passage it is evident that Quatrefages has done little more than recognise 

 the existence of a fluid in the general cavity of the body. It is true, as explained in the 

 author's Report, that in some species ova and speimatozoa are sometimes found floating 

 in this fluid. But it is not in accordance with his observations that this fluid is kept in 

 motion by cilia. In no single species are these internal cilia to be found in the general 

 peritoneal cavity. It is easy to mistake those wliich in many species clothe the bases of the 

 feet and branchiae externally, for the agents occasioning the motion of the fluid in the inte- 

 rior. Quatrefages saysnothingof the composition of this fluid, of its uses in the economy; he 

 makes no allusion to the specific differences which the floating corpuscles exhibit in different 

 species, nor does he appear to have suspected any connexion between this fluid and the true 

 blood contained in the blood-vessels. The merit of priority in the demonstration of the com- 

 position, and in the appreciation of the physiological significance of the peritoneal fluid of the 

 Annelida, is therefore claimed for the author of this Report. 



It is only possible in the larger species to obtain it in sufficient quantity for chemical ana- 

 lysis. In Terebella nebulosa, Arenicola, and the large Nereids, it may be readily collected 

 for examination. It is denser in gravity than conmion sea-water. 



In a few minutes after removal from the body of the animal, it throws down an unques- 

 tionable coagulum, like the clot of true blood. The organic corpuscles cohere into groups 

 and masses, and sink with the clot. 



