FILM KOK.MATIOX. 



127 



ill this case the fermentutive uctiuu uf the sbJiiueutui yeafit is 

 re{)hiced by respii-iitivo activity. 



When siibinergL'd in fii'sh nutrient solution, these film cells 

 pio«luce vegetations, whicli linally hehuve just like uoriual 

 sedimental yeast. Tin? rate of murj)holo};ical chanjje and adapta- 

 tion of physiological chai-acter differ witii the species of yeast. 

 In some, as was ascertiiined by 

 II. Will (Vill.), tlie cliaracter- 

 istics appertaining to the lilm 

 cells remain unimi>aireil in 

 the first new generations, and 

 in specially conspicuous ca.ses 

 several recultivatious (repeated 

 tninferences of the crop to fresh 

 nutrient solution) are required 

 in order to protluce a sedimentjil 

 yeast equal in all respects to the 

 original ance.stors of the film 

 Cells used. Notice should al.so 

 be til ken, e.ij. of an observation 

 on this point by Ed. Kaysek 

 (VI.). Further considenition 

 will be given in subsequent 

 panigraj)hs to this behaviour, 

 from the standpoint of the theory 

 of variation. 



At present we have to deal 

 with the consequences connected 

 with the pnicticiil cultivation of 

 yejust, namely the restriction of 

 film vegetiition and the exclusion 

 of cells derived therefrom. To 

 ellect this object it is nece.ssiiry 

 to keep the stock yeast in the 

 laboratory under such conditions 

 as are unfavoui-able to the 

 development of film, without 

 being at the .sjime time inimical 

 to the .sedimentjil yeast. The 



appeanince of the former may be countenictetl l)V frequent 

 tnmsferences of the cultures to fresh nutrient solutions, and 

 by keeping the culture at low tempenitures. According to 

 Hansen, the best st<ji:ige medium for prolonged use is a 10 

 per ceiit. solution of s;iccharose. In this event, however, the 

 sowing should not amount to more than a trace. When, 

 from any c^iuse, the only yeast culture available for fulfill- 

 ing an order is one that is already covered with a film, the 

 stime is suitable for direct transference to the large repro- 



Kio. 139.— Pair o( Pennauent Cell* 



(rt>iii the yi-ast riiie of a six-iiionlhs-dltl 

 »i>rt culturi- I'f Mtiiiicli li<>tt<>iii'.vca<l 

 Ni>. .•. aiul Rcrniiiiatol toa well-dcvclopctl 

 chiiiii <•( liiulii III a drup uf wurt >>ii a 

 inicri>»i-<>j>e slide in ^ixl)■•f(ll^r hours at 

 10' C. A &t.-ptuMi \\JiA fi>niied inside tl>re« 

 of the nieint>ir> i^f Iho chain. Nearly all 

 tlie cells exliiliit one or lwi> vacuole*, 

 and tile two (lernmuent cclb(D) »how an 

 even larger number. Magii. 750. (JJter 

 Will.) 



