the number of spores present. The variety of dates differs from the main form by 

 the sporangia of the latter being ellipsoidal and thickest in the middle, while in the 

 variety, on the other hand, they are just in the middle constringed, and moreover 

 by several other little salient characteristics, which only become discernible by 

 practice. 



Both, main form as well as variety produce, as the cultures grow older, a variant 

 so much deviating from the normal forms, that, if these variants were met with in 

 nature, they would certainly be proclaimed a new species if no new genus. The cells 

 are globular, and not as in the normal form elongated, but the multiplication is here 

 also exclusively effected by partition. Spores are not at all formed. 



This variant springs, so far as I have been able to find out till now, at once form 

 the normal form, which for the rest propagates unchanged, and can constantly anew 

 throw off the variant. The first variants are found in cultures which have continued 

 growing a few weeks without re-inoculating, and they go on some time multiplying 

 on the nearly exhausted culture medium, after the normal form does no more do so. This 

 points to a gain of vegetative power, at least in the conditions that prevail in the old 

 culture-medium, but in new nutriment I could observe nothing of this difference. 



The variant after repeated re-inoculation, at present already during more than 

 three years and consequently after thousands of cell-generations, has remained per- 

 fectly constant ; never could even a single sporangium be found, which, with the help 

 of the iodium reaction, can be seen at a glance in the microscopic preparation. 

 Whether in the variant the faculty of forming spores continues latent is possible, 

 even probable, but not proved. 



In the variety, isolated from dates, also occur sub-variants, that is intermediary 

 forms between normal form and variant, while in that of currants I have found no sub- 

 variants. The sub-variants still produce some sporangia, mostly 8-spored. Without 

 much trouble I could isolate from a thousand colonies three sub-variants, belonging 

 to two types; both types proved at re-inoculation to be constant, but growing older 

 they throw off, in the habitual way, the asporgene variant, so that, in order to be 

 preserved, they must be propagated from the spores. This can be done by pasteurising 

 the sowing material at 55 C., by which the vegetative cells die and the spores alone 

 survive. 



In continuing this manipulation I have obtained new sub-variants. One of these 

 produces 4- or 8-spored globular sporangia and is at first sight a new species. Cells and 

 sporangia remind of the vegetative variant which should have regained the power of 

 producing spores. But all the characteristics are limited between those of the normal 

 form and the asporogene variant. So that, although this form too is hereditary-con- 

 stant, I cannot see a new variety in it, but only a new variant. 



It is noteworthy in this case, that the variants of the same generation, that is 

 those which result from the same sowing, always differ by distinct breaks in the tint 

 of the iodium reaction, and form no flowing series between main form and main 

 variant. But I think this to be the consequence of the limited number of colonies 

 which can be overseen at each experiment, and amount to no more than one or two 

 thousand, and that it will be possible to fill up the gaps with sub-variants from other 

 cultures, which perhaps grow rarer as the leaps are smaller. The question why sub- 

 variants are so much rarer than main variants, I cannot as yet fully answer, but the 



