Organisms Consisting of One Cell 241 



plex of similarly differentiated cells." ^ This definition of 

 tissues, occurring In one of the most generally used text- 

 books of miscroscoj)ical anatomy, turns up in substance 

 again and again in tlie connnon instructional writings of the 

 day. "The foundation-stone of the tissue is the cell." ^^ 

 According to this doctrine the cell is the building-stone of 

 the tissue, so no matter what may be found within the cell, 

 it cannot be a tissue, l^ndoubtedly this way of treating the 

 term tissue has been useful, especially didactically, and 

 undoubtedly too It is on the whole justified so far as multi- 

 cellular organisms are concerned, though even here 'the 

 scientifically scrupulous teacher finds himself under the 

 necessity of doing much uncomfortable wriggling to make 

 many of the connective tissues fit into it. But when the view 

 is extended to the whole animal kingdom, to the protozoa 

 as well as to the metazoa, one sees how inadequate and 

 cramping such a conception of tissue is. 



The fact is, when we consider the real meaning of the 

 word tissue, and still further, w^ien we consider what the 

 anatomical parts are to which the early anatomists thought 

 the term could be appropriately applied, we see that with 

 the possible exception of some of the connective tissues 

 of the higher animals, we can hardly- point to a more typical 

 tissue than that of the network of strands into which the 

 peripheral sarcode of many of the Rhizopods forms itself, 

 or than the extra-capsular "plasm" of a Radiolarian like 

 ThalassicoUa. I mention this genus especially because a spe- 

 cies of it which has been well figured and described by Haec- 

 kel, is frequently used in text-books as a type of the group. 

 The "meshes constituting the sarco diet yum,"" the "alveoli 

 of the cal7/mma,*' and the pseudopodia arising in the deep 

 zone, or sarcomatrix and "forming a network through the 

 other capsular parts," are the terms in which the "plasm" 

 of these animals is described. And notice how contrary to 

 good biological usage it is to employ an anatomical nomen- 



