140 JOURNAL OF THE [December, 



all intents the "primordial utricle." It is the chemist and mod- 

 eller of this tiny workshop, for it transforms the protoplasm into 

 the cellulose which invests the mass and makes two diatoms out 

 of one. The dividing process is as follows : The hoop or band 

 widens and pushes apart the valves of the diatom and, having 

 thus performed its office, is disposed of by absorption or by be- 

 coming ruptured and then dropping off, which latter is the usual 

 way. The restriction of the hoop removed, the endochrome 

 grows rapidly. A vital ferment becomes active' in the entire 

 mass, the cellulose rind disappears or undergoes a radical modi- 

 fication, and in the body of the endochrome constriction be- 

 gins, by means of which the mass is cut through in the middle. 

 Meantime, the process which produces for each part its cellu- 

 lose film and its secretion of silica, goes on, and when absolute 

 separation takes place the one diatom has become two. This is 

 what is called cell-division. It is really a multiplication by 

 division — a process only found in the arithmetic of nature. 



But what becomes of the parent diatom ? You will notice 

 that the new diatom carries off one-half of the parent cell or 

 box. That is, one of the two is the mother valve, the other is 

 the daughter valve. You will also observe that the daughter 

 is the smaller. Though there are exceptions, yet this is really 

 a general law. When these daughter valves become in turn 

 mother valves, the old valves, then grandmothers, will die ; and 

 the daughters of this second generation will be smaller than 

 their mothers. Now, unless nature had some way of meeting 

 this point, the species would, by gradual diminution of size, be- 

 come extinct. We are all familiar with that phenomenon of old 

 age in the human race called rejuvenation — a brightening of 

 the failing faculties, as when grandmama gets her second sight. 

 Something similar takes place, I think, in the diatom. The 

 period is near when the entire individual must die. Then 

 comes a spurt of the vital force, and nature sets up a mystic 

 marriage. Two of the diatoms, we will call them old ones, 

 come together, and the phenomenon of conjugation takes place. 

 Each extrudes its endochrome, the two masses coalesce for the 

 purpose, so to speak, of bequeathing their united substance to 

 their posterity, the silicate encasing supervenes, and a diatom 

 larger than either of those which came together is produced. 

 And what about this enlarged individual ? The books, in 



