BIONOMICS. 113 



grandis) were engaged in conjugation, a single individual had, by 

 ordinary asexual division, given rise to a family of from forty tiiousand 

 to fifty tliousand individuals. Moreover, the intense internal changes 

 preparatory to fertilisation, and the general inertia during subsequent 

 reconstruction, not only involve loss of time, but expose the Infusorians 

 to great risk. Conjugation seems to involve danger and death rather 

 than to conduce to multiplication and birth. 



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

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

 {Stylonichia pttstulata] 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 con- 

 jugate 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 a vain attempt 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 com- 

 pletely 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. 



Bionomics. — 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 dying sink to the great oceanic depths, 

 form along with more substantial debris the fundamental 

 food supply in that plantless world. Fundamental, since it 



