370 



Mr. E. A. Schafer. On the Coagulation [Dec. 7, 



II. " Preliminary Notice of an Investigation into the Coagula- 

 tion of the Perivisceral Fluid of the Sea-Urchin." By E. 

 A. Schafer, F.R.S. Received November 8, 1882. 



The perivisceral fluid of the sea-urchin is a coagulable fluid of 

 about the same specific gravity and chemical composition as sea- 

 water. The corpuscles which float in it have been described by 

 several observers, and recently very carefully by Mr. P. Geddes, in 

 the " Archives de Zoologie Experimental " for 1880. The majority 

 are pale and very amoeboid, resembling the lymph-corpuscles of 

 vertebrates, a,nd the blood-corpuscles of most invertebrates. Others 

 are more granular in appearance, and others again contain a reddish- 

 brown colouring matter. The fluid in which they float is usually 

 perfectly clear and colourless when the corpuscles are separated by 

 filtration, and contains no appreciable amount of any proteid matter. 



When the fluid is drawn from the shell into a glass vessel it rapidly 

 undergoes what appears to be a sort of coagulation ; the coagulum 

 soon begins to shrink, and continues to do so to such an extent that 

 at the end of a few hours it is reduced to but a small shred of 

 coloured substance. In this respect the coagulum closely resembles 

 that of vertebrate blood, and especially of frog's blood, which may 

 also shrink in a few hours to a very small bulk. 



If the clot is examined with the microscope it is found to contain 

 all the corpuscles ; and these are so closely arranged, and their 

 processes are frequently so long and ramified, that it is difficult to 

 make out the material in which they are embedded. The material of 

 coagulation seems on this account to have been overlooked by Geddes, 

 who refers the coagulum wholly to the remarkable massing together 

 of the amoeboid pale corpuscles, which he has observed and described.* 

 It is easy, however, to demonstrate the presence of this material of 

 coagulation, and to show that the phenomenon of coagulation is inde- 

 pendent of the formation of masses or " plasmodia " of the cor- 

 puscles. 



If the fluid be mixed as it flows from the, shell with an equal 

 volume of saturated solution of sulphate of magnesia, its coagulation 

 is indefinitely delayed. With such a fluid the following experiments 

 may be made : — 



1. Diluted with water it immediately forms a coagnlum which 

 shrinks on standing as does the coagulum of the freshly drawn peri- 

 visceral fluid. The coagulum, when examined with the microscope, 

 appears as a clear substance in which the cells, which are of course 

 dead and for the most part rounded, lie separately embedded. 



2. If the mixture be filtered all the corpuscles remain on the filter, 



* Loo. cit., and " Proc. Eoy. Soc," vol. 30, p. 252. 



