62 The Mycetozoa, and 



the column, successive whorls of stalka, each carrying a 

 lateral and smaller head, as shown in Fig. 22 (6) ; each of 

 these heads finally ripens and breaks up into spores. 



The life-history of all these Acrasiece presents many very 

 curious points ; it seems to bring before us the fact that 

 separate protoplasts, without ever uniting into a plas- 

 modium or ever becoming part of a single organism, 

 may nevertheless acquire as it were the social instinct 

 and live for the good not of themselves but of the whole 

 organism, and for that purpose may submit to a divi- 

 sion of labour ; for whilst some of the protoplasts assume 

 the function of only supporting their fellows, the others 

 avail themselves of the support, raise themselves from the 

 level of their original surface, and devote themselves to the 

 fucction of reproduction. And, moreover, certain aberrant 

 and sessile forms of the Dictyostelium seem to show that this 

 elevation of a portion of the protoplasm is not necessary 

 to reproduction, though it may well be that the greater 

 exposure to the ripening influences of the atmosphere and 

 the sun may render it beneficial to the organism, and so 

 more than compensate for the withdrawing from the 

 function of reproduction of a certain part of the protoplasm, 

 and applying it to the purposes of support alone. 



UNICELLUIAB OBGANISMS. Leaving now the subject of 

 classification, and of the aberrant forms of myxies, we 

 return to the principal group. We have already dwelt 

 upon the fact that the myxies show all their vital powers 

 and all their capacity for development without the forma- 

 tion of a true cell-wall, or undergoing division by septa 



