44 Our Food Mollusks 



The new cell, called the fertilized ovum, or, better, the 

 oosperm, now begins a process of division that results in 

 a large aggregate of cells, which gradually group and 

 arrange themselves into the form of organs, in which 

 form, position, size and function, conform to the con- 

 ditions characteristic of the species. 



There is nothing in nature so marvelous as this mi- 

 nute fragment of living substance. It was formerly be- 

 lieved that the oosperm was a fully formed individual in 

 miniature, possessing all the organs of the adult body, 

 and that, like a plant bud, it merely expanded and un- 

 folded during development. In reality it is a simple cell, 

 undifferentiated in structure, and yet possessing the most 

 wonderful potentialities. If we place side by side the 

 fertilized ova of the simplest and the most highly special- 

 ized of many-celled animals, we are able to discover 

 only minor differences in structure, such as are easily ac- 

 counted for by secondary causes — a greater or less ac- 

 cumulation of yolk and the like. Even the fertilized 

 ova of plants are essentially similar to these. And yet 

 we know that each holds in its minute body, when living, 

 the hidden power to set in motion and to continue a long 

 series of marvelous transformations, ending in one case 

 in the production of a sponge, or in another of a human 

 being. The marvel of it was recognized before Paley, a 

 century ago, wrote : — " A particle, in many cases minuter 

 than all assignable, all conceivable dimensions; an aura, 

 an effluvium, an infinitesimal ; determines the organiza- 

 tion of a future body; does no less than fix whether 

 that which is about to be produced, shall be a vegetable, 

 a mere sentient, or a rational being: an oak, a frog, 

 or a philosopher." 



The oosperm possesses the power of self-division, a 



