MUSEUM OF COMPAliATIVE ZOOLOGY. 



105 



The bit of the margin figured may be regarded as typical, not only on 

 account of its symmetry, but also because of the fact that the youngest 

 individuals are placed at the normal distance from the margin. Al- 

 though I have seen these conditions 

 repeated in enough instances to assure 

 rae of their normal nature, yet, owing 

 to a crowding of polypides, both among 

 themselves and to the margin of the 

 colony, and also to the consequent dis- 

 placement of polypides, the appear- 

 ances which I am about to describe are 

 often obscured. 



First, the interrelations of the indi- 

 viduals included within compartments 

 1-8 are exactly repeated in compart- 

 ments 9-16. The same repetition 

 holds true for the remainder of this 

 side of the colony. On the opposite 

 side, the number varies from «ix to 

 eight. At the ends of the colony, 

 owing to crowding of individuals, it is 

 difficult to count with accuracy. Since 

 all individuals are derived from pre- 

 ceding ones, the conclusion seems rea- 

 sonable that the inhabitants of these 

 eight branches were derived from a 

 common ancestor. It is interesting 

 that from each of these ancestors the 

 Siime number of branches and an 

 almost equal number of individuals 

 are produced, and that the correspond- 

 ing individuals in each of these fam- 

 ilies, e. g. Figure A, 4, 5 anc* 12, 13, 

 and 7, 8 and 15, 16, are similar in 

 position, and of the same stage of development. 



Secondly, most individuals figured have given rise to two individuals ; 

 some, on the contrary, to but one. Of the two individuals produced, 

 one (the older) passes into a second (new) compartment, and so forms 

 a new branch. The younger, however, remains in the ancestral com- 

 partment, and thus continues the ancestral branch. See, e. g., individual 



FlOOKB A. 



