iv] THE SECOND GRADE 113 



with each consignment. Suppose further that while 

 printing he can instruct the distributors in such a 

 way that they will later be able to do their work 

 more soundly, then there will be collected a crowd 

 of embryo distributors at headquarters, from which 

 the fully-trained ones will from time to time depart. 



In the first stage the business is like Gymnodinium 

 pulvisculus: then like Blastodinium, and at the last 

 like Haplozoon : the division of labour has come as 

 the first forerunner of the higher development, and 

 this it has done because in both cases there are two 

 special functions to perform which cannot be per- 

 formed simultaneously by a single individual. 



The existence of two mutually exclusive necessities 

 is thus the origin of this type of higher individual : 

 at first the single cell performs them both, but at 

 the expense of not feeding while it is reproducing, not 

 reproducing while it is feeding. Again the sacrifice 

 by a part leads to improvement for the whole ; the 

 great fact once discovered that of two cells one can 

 feed for both, the other reproduce for both, and the 

 later steps follow almost as a matter of course. 



It is to be remarked that for the two functions 

 of nutrition and reproduction thus to clash with one 

 another, it must needs be that the organism can only 

 thrive in a very special and a very limited environ- 

 ment. An individuality like that of the Catenata is 

 therefore found chiefly among parasites, which exist 



H. 8 



