in] OTHER DEFINITIONS 71 



so-called "act of fertilization," was looked on as some- 

 thing which had to be repeated at regular intervals 

 to keep the race going. Somehow it communicated 

 to the organism a mysterious force, which sooner or 

 later dying down must be renewed by repetition of 

 the act. 



This is by no means a true view of sexuality. To 

 start with, one large group of organisms, the Bacteria, 

 seem not to possess it at all, while here and there in 

 higher groups it has been lost ; the American water- 

 weed (Elodea) for instance, that pest which at one 

 time choked half the waterways of England, started 

 its career in this country by being accidentally 

 imported with American timber, and in all its 

 subsequent development has never been known to 

 form seed. 



Lower down, near its first appearance, it is not 

 connected with reproduction at all, as in the Ciliates 

 among the protozoa. Hereto it is not a necessary 

 part of the life-history; Woodruff (20) has recently 

 shown that these animals, which reproduce by fission, 

 may be bred through an indefinite number of genera- 

 tions without conjugation. Enriques, on the other 

 hand (7), has shown that a ciliate which has just 

 conjugated, or in other words received a part of the 

 nucleus of another and joined it with its own, may, 

 before dividing at all, and with this very nucleus just 

 formed by sexual fusion, immediately repeat the 



