188 THE MICROSCOPE. Dec. 



dosmose and exosmose theory as sufficient to account for the 

 many and curious variations of movement which I have ob- 

 served among the diatoms. 



I received a card from the Editor of the A. M. M. J. asking 

 me to send him a communication upon the subject of the Biol- 

 ogy of the Diatom, and althougli I liad half promised what T 

 am now engaged upon for the R. M. Society's Journal, [ am 

 tempted to accept his offer to take part in the interesting dis- 

 cussion in his columns. 



It so happened that when on reading your article in the A. 

 M. M. J., I wrote to you asking where I could obtain Prof. 

 Smith's paper from which you had quoted, I had got half 

 through an article illustrated by numerous drawings with the 

 camera lucida, in which I sought to show tbit my own recent 

 observations tended to throw doubt upon Dr. Miquel's conten- 

 tion in " Le Diatomiste " and to somewhat strengthen Count 

 Castracane's objection to the theory that what since the Rev. W. 

 Smith's time has been generally regarded as a sporangia! frus- 

 tule which is destined to perish after fulfilling the duties of a 

 spore case, is in fact a simple i)rocess of nature which takes 

 place for the purpose of the recovery of the size of the diatom 

 diminished to its minimum as a life supporting body by re- 

 peated subdivisions. The phenomena which I considered as 

 opposed to the size recovering theory, and as supporting the 

 spore theory were shown very clearly in a gathering which I 

 made last spring and from which I had mounted several dozen 

 successful slides from which my drawings were made. They 

 consisted of (1), many cases of formation of mega-frustules from 

 many sizes of parent frustules of cocconeraa, there being many 

 specimens of frustules of the same species in the gathering of 

 zies considerably below the size which produced the mega-frus- 

 tule and which Dr. Miquel speaks of as the minimum size 

 which necessitates the auxospore and (2) many hyaline cysts la 

 the same gathering as that in which the formation of the mega- 

 frustules are so numerous which cysts apparently perfect and 

 unbroken enclose, in many instances closely packed together 

 numerous frustules of almost every size down to the most minute 

 of Cocconema and Gomphonema mixed and unmixed and free 

 from all extraneous matter. Prof. Smith's mention in his paper 

 of a similar observation by himself {he curiously enough sa^ 



