200 Transactions of the Society. 



so that wlieii the time for motion came the flagella had attained 

 their normal length. 



This will be seen in plate VIII. figs. 4, 5, 6, where at a, h, c, the 

 origin of the flagella in Folyioma uvella will be seen to be in the 

 nucleus, and their relative growth will be found to be greater than 

 that of the body-sarcode. This is a typical case. In each of the 

 four organisms, the same facts were discoverable in the development 

 of the nucleus, the origin of the flagella, and the growth of the body. 

 They were best seen in Tetramitus rostratus and Polytoma uvella : 

 not quite so well in Ballingeria Drysdali* and least perfectly in 

 Heteromita rostrata ; but in all they were seen with sufficient 

 clearness to leave no doubt. 



Not less interesting and striking are the minute phenomena 

 accompanying fission. In about five minutes after the adult stage 

 is reached, on the average, the act of self-division commences, and, 

 with about the same interval, each divided organism again divides 

 for hours in succession. The first symptom that fission had 

 begun was, up to about five years ago, discoverable by us only in 

 the general body-substance. But with the lenses we can now 

 employ it is clearly demonstrable that the earliest fissional activity 

 takes places in the nucleus. In Tetramitus rostratus, for example, 

 the first indication we could by any efi'ort discover was an amoeboid 

 condition of the general sarcode as seen in plate IX. fig. 1. 

 This was followed by a sudden slit at the root of the flagella, 

 fig. 2 a, causing the four flagella to be divided into tivo pairs, 

 which rapidly receded from each other ; this slit was shared by 

 the nucleus as seen at h, fig. 2, and from this time the nuclear 

 division went on concurrently with that of the somatic sarcode, as 

 seen in figs. 3 and 4, and more fully detailed in the paper read 

 before you on this organism. 



In like manner with Ballingeria Drysdali, one of the later, 

 and most carefully studied forms, the first definite trace of the act of 

 self-division was in the splitting of the beak and flagellum, plate IX. 

 fig. 5 a ; an incision almost constantly followed by a corresponding 

 incision at h, fig. 6, and this was carried into the nucleus. Almost 

 simultaneously with this, a white line appeared right through the 

 dividing organism as seen at fig. 7, and as already recorded 

 and figured.f But in all the four cases with which I am dealing, 

 it can now be shown by the employment of the new lenses of 

 great aperture, that it is the nucleus that is first, and very pro- 

 foundly, afiected. 



It must be understood that to discover the facts in the living 

 form is not by any process easy. All the finer properties of the 



* Of. Kent's ' Infusoria,' vol. i. p. 310 et seq. 



t 'Oh the Lifu-history of a Septic Organism,' by Rev. W. H. Dallinger. 

 Proc. Roy. Soc , xxviii. (1878) pp. 332-50 (2 pis.). 



