CELLS. 



53 



but which may also continue alone. Even in the common endogenous 

 cell-development (and also 

 in the cleavage process) we 

 not unfrequently observe 

 three and four nuclei in a 

 parent cell, so that then, 

 instead of two secondary 

 cells, many arise at once, 

 e. g. in the hepatic cells of 

 embryos. In certain ani- 

 mals [CucuUamis, Ascaris 

 dentata, Distoma, Cestoi- 

 dea), instead of cleavage 

 masses, nuclei alone are 

 developed in the first stages 

 of development, and it is 

 only later, when by succes- i 

 sive endogenous multiplica- 

 tion these have increased to 

 a great bulk, that they be- 

 come surrounded by cell 

 membranes. Something 

 similar appears to take 

 place in the cells of the 

 germ in the Crustacea, in which 10-20 nuclei are often found (Rathke, 

 ' De Anim. Crustac. gen.,' Regim. fis. 7 



1844.) On the other hand, the nu- 

 merous nuclei in the spermatic cells 

 of most animals are, in general, in 

 no way connected with cell-develop- 

 ment, since the spermatic filaments 

 are developed in them ; and the like 

 holds good of those cells of the lower 

 animals, whose multitudinous nuclei 

 are changed into thread-cells. The 

 import of the number of nuclei in 

 certain nerve-cells, and in the large 

 cells of the bone-medulla, which Robin and I have observed, is doubt- 

 ful ; in the latter, I think it is not improbable that the multiplication 



Fig. G. — Cartilage cells from a fibroii?, velvety, articular cartilage of the condyle of the 

 femur of man, magnified 350 diameters; all lying in a fibrous matrix, and readily isolated: 

 a, simple cells, with or without a thickened wall, with 1 or 2 nuclei; b, secondary cells, or 

 cells of the first generation, with 1 or 2 nuclei; 1, 2-5 or more, in parent cells; b, c, cells 

 of the second generation, 1-3 in number, in cells of the first ; d, freed groups of secondary cells. 



Fig. 7. — a. Peculiar granulated cells with many nuclei from the youngest medullary cavi- 

 ties of the flat bones of the skull in man. Magnified 350 diameters. 



«r' 



