io6 



GENERAL PRINCIPLES OF ZOOLOGY. 



the blood-cells, are distinguished as red and white blood- 

 corpuscles. The latter, the 

 leucocytes, are present in small- 

 er numbers and have great 

 similarity to the amoebae found 

 in water; they are lumps of 

 protoplasm, contain a nucleus, 

 devour foreign bodies, as, for 

 example, carmine granules in- 

 jected into the blood, and move 

 in the "amoeboid' manner, 

 i.e., by putting out pseuopodia 

 (Fig. 43)- 



Red Blood-corpuscles. - 

 The red blood-corpuscles of 



vertebrates (Fig. 44), in the mature condition, are circular 

 or oval disks, which by objective influences, e.g., by 

 pressure, may momentarily be bent, incised, or otherwise 



FIG. 43. White blood-corpuscles, a, of 



^iKSglpI*' ^.v^r ^ " (Je 



FIG. 44. Red blood-corpuscles, a, of man; 6, of the camel; c, of the adder; d', of Proteus 

 (seen from the edge); d", surface view; e, of a ray; /, of Petromyzon; n, nucleus (all 

 the blood-corpuscles are magnified 700 times, except d, which is magnified 350 times). 



modified in form, but cannot actively change their shape, 

 because they no longer consist of protoplasm. Embryo- 

 logically they arise from true, nucleated, protoplasmic 

 cells; whether these cells are identical with the leucocytes 

 is still undetermined; but later the protoplasmic cell- 

 body changes completely into a plasmic product, the 

 stroma of the blood-corpuscle. If in this metamorphosis 

 the nucleus is retained, there is formed in the centre of 



