The Structure of Diatoms. By Dr. J. H. L. Flogel. 685 



spectra as diatoms produce, and that therefore the microscopical 

 image is unrehable, and that for this reason no Microscope could 

 clear up the true facts. The first portion of the sentence 1 admit, 

 but the second I deny. That the half wave-length of light in 

 praxis indicates the limit beyond which in 1869 no Microscope 

 showed details, I had clearly demonstrated in my paper on the 

 optical appearances in diatoms (5) ; the great honour of having 

 proved theoretically the existence of this limit is due to Prof. 

 Abbe. I had surmised conclusions on the results of my diffraction 

 studies on the liner sculpture details, which 1 considered unreliable 

 after having successfully used the section method. Several other 

 objects furnish diffraction-spectra, although they are of totally 

 different sculpture which we cannot bring into parallel with the 

 diatoms: for instance, butterfly-scales,* and the skin of the 

 Ascarides whose diffraction phenomena have been studied by 

 Leuckart (12, vol. ii. p. 164). From the latter nobody can arrive at 

 definite conclusions on the sculpture; but it would be wrong to 

 assert that no Microscope in the world could elucidate it. Summing 

 up we may say : the diffraction phenomena suggest only the 

 existence of small particles of approximately equal size in layers, 

 but they convey nothing as to their form or arrangement. The 

 diffraction theory does not put a stop to the closer investigation of 

 the sculpture of muscles, diatoms, &c., and Abbe's assertion that 

 we could never arrive at anything reliable about this sculpture is 

 unfounded and was practically refuted at the time he published it. 

 With this I believe to have given sufiicient courage to all timid 

 students to continue their researches which otherwise would be 

 without prospect as long as Abbe's opinion predominated. 



The latest work by Prof Strasburger (27, p. 143) treating of 

 the sculpture of the cell-wall of diatoms, mentions me with the very 

 unflattering sentence — " Fldgel believed he had found out that the 

 ceU-wall contained chambers opening above as well as below." 

 Then comes 0. Miiller who proves the opening with Triceratium. 

 I may expect that Prof. Strasburger after reading my present 

 work will alter his views considerably. Should I be disappointed 

 therein the way would be open to him to investigate the matter 

 himself personally, and I o\\n that among all living botanists, I 

 consider Lim to be the most able to assist in solving the question. 

 Should he in such case also " believe " he has arrived at results 

 slightly different from mine, I would request him before presenting 

 the world with his results to try again a second and a third time 

 with different weather, with other sections, and with other physical 

 disposition personally, and then he will soon convince himself that 

 his former "belief" was unbelief. 



* About tlioir finer sculpture I hIiuII publisli my investigations sliortly in a 

 zoological journal. 



