'^^, 



d 



^'^'^^^Sm 





)k 



ox 



?Jy the 



Efistjlh I 



process 



d several ti 

 pointed me 



nstead of ( 



Gr 



s: 



ti| 



■en partly diie: 



^h to suit 



ly that, as tait 

 'ct Infusorial 



-thatis,l)Tt 



1, fission, r 



,ryos. Uf 



y 



arious 



and whf« 



clowly 



tlie smalls' 



: be «' 



ither 



lo*' 



1) 



[thep 



rflces' 



Z^^ BEGINNINGS OF LIFE. 



293 



MM 



Lach- 



cess of fission in Oxytricha, says ^ that « some hours ' 

 are required for its completion in large individuals. 



Though the development of "^ova' in the Infusoria 

 by a sexual process of generation seems now to be 

 generally accepted, on the faith of the recent researthes 

 of Balbiani and those of 

 mann^ no appeal can be made to such a process of re- 

 production in order to account for the rapid appearance 

 of multitudes of Infusoria in organic solutions. Even 

 those observers whose labours have tended to establish 

 the reality of the process^ do not pretend that it is an 

 ordinary mode of multiplication. On the contrary^ they 

 maintain that it is an extraordinary method of increase 



r 



to which the animal resorts occasionally under the 

 pressure of adverse circumstances ^. The rate of in- 

 crease^ also, could only be extremely slow 

 method, since the animals remain in contact for five 

 or six days, and it is not till a further lapse of two or 



+ 



three days that the ^ova"* obviously begin to make their 

 appearance-^. Balbiani's observations were principally 



this 



^ 'Ann. des Sc. Nat/ 1853, p. 122. 



^ When speaking of the process of fissiparous division, M. Balbiani 

 says (loc. cit. p. 1194) : — * Nous avons effectivement constats que ce mode 

 de propagation avait des linaites et se terminait invariablement de Tune 

 des trois maniferes suivantes : ou part la mort naturelle et presque simul- 

 tanee de tous les individus appartenant k une meme cycle, ou par le 

 retour de la generation sexuelle indiquant la fermeture d un de ces cycles 

 et le commencement d'un cycle nouveau, ou enfin par le phenomena de 

 renkystement.' 



^ 'Journal de Physiologic,' 1858, torn. i. p. 346. The process is 

 doubtful in nature ; and from the absence of all sexual organs in the two 



