6i4 Lor and e Loss Woodruff. 



and believes that this should be sharply distinguished from the 

 fine honey-comb structure which obtains in other forms, such as 

 many of the hypotrichida; and he regards the observations of 

 Sterici ('78), that Stylonychia mytilus has a markedly vacuolized 

 structure, as an indication of abnormality. Simpson ('01, 2) 

 made sections of what he regards as "absolutely normal" 

 Stylonychia, and he states that they "showed the vacuolization 

 fairly well developed. . . ." Again, the question of the fixity 

 of form and position of the macronucleus has been variously dis- 

 cussed since Balbiani more than forty years ago observed a shifting 

 in Paramcecium, to its recent consideration by Simpson through 

 observations on various species. My own cultures give conclusive 

 proof that the cytoplasm becomes considerably more vacuolated 

 at certain periods in the life-cycle; but further, daily observation 

 has shown that hardly any two individuals are identical in their 

 cytoplasmic condition, and the same can be said of the position 

 of the macronuclei and the accompanying micronuclei. 



The fact that subjection to beef-extract gradually revived the 

 cellular activity and caused the resumption of the normal condi- 

 tion of cytoplasm and nuclei, shows that up to the verge of extinc- 

 tion the cell-life can be revivified. I think this indicates that we 

 are hardly justified in assuming that Protozoa, when dividing at a 

 low rate, with nuclei fragmented, etc., are exactly "abnormal." 

 The fact that it is possible to restore such remarkable types as \ 

 have figured to the text-book "normal" condition suggests that 

 we are justified in regarding these changes as phases in the life- 

 history of the Infusoria which occur under certain conditions after 

 a considerable period of vegetative reproduction. 



VI. EFFECT OF INITIAL AND DAILY STIMULATION WITH SALTS 

 ON THE RATE OF DIVISION. 



The first essential for experimental work with salts on the 

 fission-rate of Protozoa is to have a constant subject on which the 

 stimuli are to be applied so that the results obtained shall be 

 directly comparable. This condition is admirably fulfilled by 

 cultures of Infusoria fed daily on the same diet and carried on in 

 this way for many weeks; and such cultures probably afford as 

 near a perfect "control" as it is possible to get for work of this 

 kind. 



