Our delations. 9 



present- generation. Tf they prove to be only first cousins the diver- 

 gence took place t\vo generations ago. As between a German and ;i 

 Scandinavian the divergence may have taken place from 100 to 500 

 gem-rations ago ; as between a Frenchman and a Chinaman 10 or 20 

 times as Ion;;- ago. As between the man and the ape; the ape and the 

 carnivore; the carnivore and the marsupial; the marsupial and themono- 

 tremc; the monotrcme and the amphibian; the amphibian and the fishes; 

 the fishes .rind the; tunicate; the tunicate and the worm; the worm and 

 the zoophyte; the zoophyte and the protozoan the periods when they 

 diverged from each other to become the ancestors of the present races, 

 must be reckoned the first by myriads of ages, and the last by those 

 enormous geological epochs and cycles that bewilder and overpower the 

 imagination by their vastness. 



CHAPTER III. 



EMBRYOLOGY. 



Among the phenomena that tend to prove the common origin and 

 blood relationship, the most striking are those concerned in the prenatal 

 development of the individual. Every animal, including every man, 

 begins existence as a nucleated cell, or, as it might be called, a nucle- 

 ated globule of protoplasm. These nucleated cells are extremely 

 minute, a common size being about the 1-120 of an inch in diameter. 

 They consist of a bit of protoplasm in which, but not usually in the 

 center, is the nucleus. In this nucleus is a still more minute dark spot 

 called the nuclcolus or germ spot. Protoplasm is composed of four 

 elementary substances : oxygen, hydrogen, nitrogen and carbon. These 

 form the binary compounds, carbonic acid, water, ammonia, from which 

 the protoplasm of plants is formed. 



FIG. 7. Moneron (Protamoeba) in act of re- 

 production. 



A. The whole moneron which moves like 

 the amoeba by expanding 1 and contracting its 

 jelly like substance. 



B. The sumo partly pinched in two. 



C. The business accomplished and two new 

 ones formed from the old one. 



FIG. 7. 



The higher animals cannot live on carbonic acid, water and ammonia 

 in their simple condition, although nothing more than these enter into 

 the composition of many of the simpler forms of animal life, and the} r 

 contain the chief elements required for all forms. But from the plants 

 is obtained the protoplasm from which animal cells are formed. The 

 simplest animals, the protozoa, consist of only one cell. This cell 

 grows in size by absorbing protoplasm from some vegetable matter, and 

 when it reaches maturity it divides into two parts, each part becoming a 



