46 THE DOCTRINE OF IMMORTALITY 



are created from a single egg. This phenomenon is termed 

 polyembryony. It was surprising to discover recently that 

 polyembryony occurs in a mammal. In the year 1885 Von 

 Jhering observed that the armadillo regularly produces four 

 embryos in one sac, and he expressed the supposition that they 

 arise from a single ovum. Professor Patterson 18 of the Uni- 

 versity of Texas has studied the phenomenon carefully in a 

 species which occurs in Texas. The development of ordinary 

 mammals begins with the formation of a small vesicle. At 

 one pole of this vesicle there accumulate a small number of cells 

 in which no differentiation is recognizable. The accumula- 

 tion is termed the germinal disc and produces the embryo. 

 Patterson obtained eggs of the armadillo in- the vesicular stage, 

 and found upon each vesicle four distinct germs discs. Each 

 disc forms an embryo. Thus it becomes certain that in this 

 mammal four embryos, always of the same sex, arise from 

 one ovum. 



It is also possible to cause artificial polyembryony with 

 certain eggs. When an egg begins its development, it divides 

 and when the egg is small the division usually produces two 

 cells alike in size. Driesch 19 was the first to make the interest- 

 ing experiment so to shake an egg in the two-called stage 

 that the two cells were separated from one another. Under 

 favorable conditions each of the separated cells forms an 

 embryo. The original experiment was made with the eggs of 

 sea urchins. The artificial polyembryos do not attain a nor- 

 mal size, and therefore do not develop quite as do the natural 

 embryos. The experiments of Driesch have been repeated by 

 many Americans and much extended, and indeed with such 

 eagerness that for a certain period we ^termed our embryolo- 

 gists " egg Shakers. " You know probably that the Shakers are 

 a Quaker sect, dedicated to celibacy. 



