252 SUMMARY OF CURRENT RESEARCHES RELATING TO 



specific gravity is 1026, or tlae same as that of sea-water ; it has an 

 alkaline reaction, and contains a minute quantity of albuminoid 

 matter. It rapidly undergoes coagulation, and the corpuscles form a 

 clot, which, considerable at first, contracts very rapidly. 



The white corpuscles are of two kinds. One is that of an amoe- 

 boid nucleated cell, the protoplasm of which is finely granular ; the 

 pseudopodia are long, filiform, and branched, or are united with one 

 another to form rings, and the two kinds of pseudopodia may be found 

 in one corpuscle. Extreme tyjies appear only to be developed during 

 the gradual death of the animal. The annular disposition of the 

 pseudopodia appears to be characteristic of the Echinodermata ; 

 Semper has noticed it in the Holothuroida, and Mr. Geddes has 

 observed it in Ophiurida and Comatula, but never in any other 

 invertebrates. 



When the corpuscles unite, they do so thus : the pseudopodia of 

 one corpuscle touch and unite with those of one of their neighbours, 

 and then the corpuscles approach one another and soon form a single 

 homogeneous mass. This new body seizes on all the corpuscles with 

 which it meets, incorporates them, and grows like a rolling snowball. 

 Thus there are produced vast plasmodia, which soon become difieren- 

 tiated into a transparent homogeneous ectosarc and a granular endo- 

 sarc. The latter contains foreign bodies. 



This Plasmodium, or composite amoeba, now takes on a new form 

 of activity ; the ectosarc gives off j)seudopodia of extraordinary length, 

 which ramify and anastomose. These pseudopodia are genei'ally 

 filiform. 



If we seek to compare the corpuscles of organized fluids with the 

 Protozoa, we must not limit ourselves to the ordinary Amceba, but 

 must take into account such forms as Protomyxa or Myxomycetes ; 

 when we do this, we get the following comparative table : — 



Corpuscles. Myxomycetes. 



1. Development by transverse division. 1. By endogenous division. 



2. Flagellated cell (mastigopod). 2. Mastigopoda. 



3. Amoeboid cell (myxopod). 3. Myxopoda. 



4. Mobile plasmodium (produced under 4. Mobile plasmodium. 



fresh conditions). 



5. Immobile sphseroid. 5. Immobile sphferoid. 



6. Death. 6. Encystation and fresh division. 



The author is of opinion that the theory which looks on the 

 amoeboid character as being a fundamental character of the animal 

 cell is fully justified. 



Coming now to the second and rarer type of white blood-cor- 

 puscle, we find it to be larger and to be filled with large spherical 

 refractive granules, which obscure the presence of the nucleus. The 

 delicate pseudopodia are short ; they resemble the mucous cells which 

 Semper detected in the Holothurians, and they are the coarsely granu- 

 lated corpuscles in vertebrated as well as in invertebrated animals. 



The most interesting corpuscles are those coloured brown, which 

 the author has never detected in any other Echinoderms than the 



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