56 



TERATOLOGY OF DIATOMS. 



appreciable, and not unfrequently these box-shaped diatoms look some- 

 what like flexible accordions which are in the act of being pressed in.- 

 This bizarre morphology does not prevent these cell monstrosities from 

 living and having a perfect endochrome. 



" The results obtained with teratological cultivations strike me as very 

 remarkable. They explain, in the first place, how it comes about that 

 diatoms of abnormal form are met with in nature ; it would seem that 

 if only the growth of diatoms could be successfully arrested when they 

 assumed the peculiar forms already indicated, not only could an infinite 

 number of hybrid varieties cf the same species be created, but perhaps 

 also the series of modifications could be followed, which slowly give rise 

 to the transference from one species to another. So far I only feel con- 

 fident on this one point, viz., that it is possible to produce very great 

 deformities in the silicious carapaces of diatoms by means of cultivation." 



Every diatomist has occasionally come across deformed or modified 

 valves and many of them have collected curious forms. The collection 

 of Mr. E. Weissflog includes a large number of them. Amongst the most 

 curious are the three figured below. 



/ 



Fig. 19. Deformed Diatoms. 



No. i represents a Navicula permagna, the half of the raphe of which is 

 wanting, whilst in the same part of the valve the striae are radiant ; No. 2 is 

 a figure of an abnormal Navicula maculata in which the raphe is present 

 only for a short distance, while the striae become still more radiant and 

 the valve assumes an almost oval outline. Lastly, in No. 3 the two raphes 



