THE LIFE CYCLE 



335 



season when the shoal waters in which they grow 



evaporate. While they are 

 often spoken of as seed- 

 like bodies, they are wholly 

 unlike seeds in that they 

 contain no embryo, and 

 they are entirely different 

 in origin. During the 

 growing season, (spring and 

 early summer) , little groups 

 of cells become segregated 

 within the tissues of the 

 parent animal (fig. i88&), 

 and become invested there 

 with a common protective 

 covering, the statoblast 

 wall, that is often of re- 

 markably complicated and 

 beautiful structure. When 

 the parent dies and its flesh 

 disintegrates, the stato- 

 blasts are liberated, to be 

 carried about with the 

 waters, or blown about 

 with the dust of the dessi- 

 cated bottom mud, or, in 

 the case of statoblasts pro- 

 vided with grappling hooks, such as those of Pectinatella, 

 to be carried and distributed by aquatic animals. In the 

 Spring, those favorably situated germinate and develop new 

 colonies of the parent form. 



Statoblasts occur in groups most of whose members are 

 marine. They are probably an adaptation of the life cycle 

 to the conditions imposed by shoal and impermanent 



FIG. 188. Plumatella a a small colony 

 growing on a submerged stick; b, a 

 single branch, with 



all 



art of 



gle 



three individuals in different states of 

 contraction; i, anus; j, intestine (U- 

 shaped) ; k, statoblast developing; /, 

 lophopore (crest of tentacles) ; m, 

 esophagus: n, the chitinous sheath that 



l, (after Allman) 



esophagus: n, t 

 shelters an indi 



