Ii8 PHYLUM PROTOZOA THE SIMPLEST ANIMALS. 



The riddle was, in part at least, solved by a long series of careful 

 observations. In November 1885, M. Maupas isolated an Infusorian 

 (Stylonickia pustulata\ and observed its generations till March 1886. 

 By that time there had been two hundred and fifteen generations pro- 

 duced by ordinary division, and since these lowly organisms do not 

 conjugate with near relatives, there had been no conjugation. 



What was the result? At the date referred to, the family was 

 observed to have exhausted itself. The members were being born old 

 and debilitated. The asexual division came to a standstill, and the 

 powers of nutrition were lost. 



Meanwhile, before the generations had exhausted themselves, several 

 of the individuals had been restored to their natural conditions, where 

 they conjugated with unrelated forms of the same species. One of 

 these was again isolated, and watched for five months. In this case, 

 up till the one hundred and thirtieth generation, it was found that on 

 removal to fresh conditions the organisms were capable of conjugating 

 with unrelated forms. Later this power was lost, and at the one 

 hundred and eightieth generation the individuals of the same family 

 were observed making vain attempts to conjugate with each 

 other. 



We thus see that without normal conjugation the whole family 

 becomes senile, degenerates both morphologically and physiologically. 

 Morphologically, the individuals decrease in size, until they measure 

 only a quarter of their original proportions, the micronucleus atrophies 

 completely or partially, the chromatin of the macronucleus gradually 

 disappears, other internal structures also degenerate. Physiologically, 

 the powers of nutrition, division, and conjugation come to a standstill, 

 and this senile decay of the isolated individuals or family inevitably 

 ends in death. 



The general conclusion is evident. Sexual union in those Infusorians, 

 dangerous, perhaps, for the individual life, and a loss of time so far as 

 immediate multiplication is concerned, is absolutely necessary for the 

 species. The life runs in strictly limited cycles of asexual division. 

 Conjugation with allied forms must occur, else the whole life ebbs. 

 Without it, the Protozoa, which some have called "immortal," die a 

 natural death. Conjugation is the necessary condition of their eternal 

 youth. 



It must be noted, however, that some subsequent investigators have 

 watched over two hundred asexual generations of ciliated Infusorians 

 without seeing the slightest trace of senile degeneration. Calkins has 

 cultivated Paramcecium for over six hundred generations without 

 conjugation by giving beef extract when degeneration threatened to set 

 in. The same result was obtained by stimulating with alcohol, 

 strychnine, etc. 



(Ecology. Many Protozoa raise organic debris once more 

 into the circle of life, and many form part of the food 

 of higher animals. Thus those pelagic Foraminifera and 

 Radiolarians, which sink dying to the great oceanic depths, 

 form along with more substantial debris the fundamental 



