The Microscope. 203^ 



stitutes a whole capable of acting by itself and for itself; it is 

 endowed with an individuality proper to itself. This is not only 

 true for unicellular beings, but also for the cells composing higher 

 beings, provided however that the cells possess the necessary 

 conditions to display their activity, which often requires the 

 concurrence of other cells, of tissues, and even of the whole 

 being. 



Closely related to this question is that of cell-fusion. For my 

 purpose however it is sufficient to state that b}' the fusion of 

 cells the individuality may be lost, but that this is not a neces- 

 sary consequence. Thus for example, in fertilization the male 

 cell and the female cell fuse so perfectly together, protoplasm 

 with protoplasm and nucleus with nucleus, that the individuality 

 of each cell is lost, and the result is a new individual, the so 

 called cell of segmentation. 



In forming a plasmodium, cells that have been free sometimes 

 fuse in great numbers, but this fusion is not so perfect as in the 

 case of the union of the germ cell with the sperm cell ; for here 

 protoplasm fuses with protoplasm and nucleus with nucleus, but 

 in the case of a plasmodium the nuclei remain distinct, and the 

 cell has the appearance of being an ordinary multinucleated 

 cell ; in this case also, the individuality of each cell has been 

 lost. Examples of the same kind are presented by the Myx- 

 omycetes, lactiferous tissue, and particularly in the sporangia of 

 many plants. In many other cases however, the fusion between 

 cells is only at the points where they touch each other, and the 

 cells then do not lose their individuality ; they still act for them- 

 selves. Cases of this kind are rather common ; for example, 

 muscle cells fuse with cells of glands, and nerve cells with cells 

 of muscles. 



Fromann believes that he has been able to trace a connection 

 of the protoplasm through the walls of adjacent cells, and hence 

 some biologists believe in the continuity of protoplasm. If such 

 be the case in any plant, then such a plant may be considered 

 as a variety of plasmodium. Another difficulty we meet in the 

 Coeloblasta', especially in the genera Cmderpa, Botrj/diimi and 

 Vaucheria. Here we find large and sometimes branching fila- 

 ments without partition walls. Sachs consider them as simple 

 cells which may be multinucleated, whilst others consider them 

 as cellular filaments in which the partition cell-walls have never 



