Evidence from Protozoans 385 



like origin. 



So here again, as in the flagella of various flagellates, and 

 the trichocysts of Frontonia, we find both chromatic and 

 n on- chromatic substances of the cell acting as the physical 

 basis of heredity. 



(g) The Shells of Foraminifera 



Some of the most striking examples of what may be called 

 general cytoplasmic activity in the production of heredity 

 structures are furnished by many of the shell-forming Fora- 

 minifera. The case of Euglypha alvcolata may be taken 

 as illustrative. I take this animal not only because its re- 

 production is a telling case in favor of my general conten- 

 tion, but also because it is often used in text-books and 

 other general zoological works, and so is readily available 

 for study so far as literature is concerned. As shown by 

 figure 27 a, b, c, d, e, the animal is egg-shaped, of regular 

 outline, and enclosed, except for an opening at the small 

 end, in a thin shell made up of little plates. The plates 

 are silicious and are glued by a substance supposed to be 

 silicious. The mode of reproduction exhibited is usually 

 considered to be a form of budding. By examining the fig- 

 ures in connection with the following description taken from 

 Calkins, the points of chief interest will be readily seen. 

 "This bud (b) grows until it has reached its definitive size 

 (usually about that of the original cell) when the shell- 

 coating for the new individual * is deposited. The build- 

 ing material for the shell of the daughter-individual is 

 formed within the protoplasm of the maternal cell (r.s.p.). 

 If regular plates of silica or chitin, these plates are secreted 

 long before division and stored up in the protoplasm which 

 surrounds the nucleus (Euglypha, Quadrula,). If quartz 

 crystals, or any other foreign bodies, these particles are 

 picked up and stored in similar manner, to be used later for 



