172 The Field Naturalist's Quarterly May 



water is swallowed with the food, which at first appears to be sur- 

 rounded by a ring of clear fluid, — the rest of the protoplasm always 

 appears granular, — but the water quickly diffuses itself, when the clear 

 ring vanishes. 



The function of reproduction is also the simplest imaginable. The 

 Amoeba feeds, and grows. Then the animal just divides itself into two, 

 each half walking away a separate and complete Amoeba ! This is 

 repeated ad infinitum. 



Glancing back over the above paragraphs, we see that the three 

 functions of Relation, Nutrition, and Reproduction are all performed by 

 one and the same parts of the Amoeba — the body-substance, or proto- 

 plasm. We do not find one portion set apart to act as a mouth, another 

 as a vent, another as a foot, another as an ovary, &c. There is, in 

 short, a complete absence of specialisation — any part will perform any 

 function. In the course of this series of papers on Field Zoology we 

 shall have other types of animals described, and shall see how, as we 

 rise higher and higher in the scale, each group is more and more special- 

 ised, and not only are special organs set apart for particular functions, 

 but special individuals are set apart each with its own particular organs, 

 whilst another set of individuals have other organs, the complement of 

 the first, — we call them male and female. 



Amongst the Protozoa we have no certain indication of sex. Very 

 rarely, conjugation and fusion of two individuals have been observed, and 

 this has been interpreted as a kind of sexual reproduction. I have seen 

 this in some of the higher infusoria (Stylonichia, e.g.), but not in 

 Amoeba. Yet, though we cannot detect any indication of sex, this 

 occasional conjugation of two individuals has a significance of the 

 greatest interest in relation to certain phenomena of reproduction in 

 the higher animals. Amongst these latter it is notorious that inter- 

 breeding between near relatives, if continued for several generations 

 without the introduction of "new blood," leads to deterioration in the 

 physique of the race, and, not uncommonly, to eventual extinction. 

 Public attention has recently been called to an instance in the case 

 of the wild cattle at Chartley Park. 



In the same way it has been found that the Protozoa will multiply by 

 fission at an almost incredible rate as long as food is abundant, but that 

 eventually, unless conjugation takes place between individuals which are 

 not near relatives, the race deteriorates and dies out. This was proved 

 by a long series of careful experiments by a French scientist, M. 

 Maupas, who isolated an infusorian and observed its generations for 

 a period of five months. By that time there had been 2 1 5 gen- 

 erations produced by division, and since these lowly organisms do 

 not conjugate with near relatives there had been no fusion of two 

 individuals. The result was that the family had exhausted itself. They 

 were not old exactly, but were being born old. Self-division came to 

 a standstill and the power of nutrition was lost. Meanwhile several 

 individuals which had been removed to another basin conjugated with 

 unrelated ones of the same species. One of these was isolated and 

 watched for five months. The usual richness of successive generations 



