entr' acte 205 



her telegraph system as it acts in the nerve-fibers. We 

 keep asking questions, but many remain unanswered. 



We ought to know more, we cannot be satisfied yet; the 

 play must go on. We search for other members for our 

 cast but they are hard to find. Many other attempts to 

 unravel the puzzle of life have been undertaken, but were 

 only partly successful. We cannot review them all, but- 

 let us select two which seem promising: artificial partheno- 

 genesis, and the mitogenic rays. 



ARTIFICIAL PARTHENOGENESIS 



Parthenogenesis is one of those high-sounding Greek 

 terms that are nevertheless easy to understand. It means 

 literally birth by a virgin. It signifies the initiation of 

 development of a new animal solely from the female of a 

 species, without fertilization by a male. Artificial parthen- 

 ogenesis means that the process is brought about by some 

 agent in the laboratory; natural parthenogenesis means 

 that it occurs normally. 



Every animal, with the exception of the very lowest 

 forms of life, develops from the egg-cell or ovum which has 

 grown in the ovary of the female animal. Before it can 

 develop, it must unite with the germ-cell of the male which 

 is motile and known as the spermatozoon. The develop- 

 ment of the fertilized ovum occurs in the body of the female 

 animal (that is in mammals) where it is nourished by the 

 mother's blood until birth. In birds and reptiles the fer- 

 tilized ovum is deposited in an egg which contains an over- 

 abundance of nutrient matter around the microscopic germ- 

 cell. In every case, the ovum or germ-cell is of microscopic 

 size, usually barely visible to the naked eye as a diminutive 

 dot, never corresponding to the size of the animal which 

 develops from it. A whale or an elephant develops from a 

 germ-cell which is not very much larger than that of a 

 mouse. This development may appear as the most baf- 

 fling wonder of nature but it loses some of its miraculous 



