-I M KI'TIHIUTY 1\ IIM)ROIDS. 



c.tmpanularian, Obelia, the earlier stages are in general more 

 susceptible than the later, though some differences depending 

 on motor activity and on position in the colony (pp. 112-117) 

 appear. 



The earliest stages of bud development (Fig. 9, a, Fig. 10, g, 

 are, with rare exceptions, less susceptible than naked early hy- 



8 



FIGS. 7-9. Pennaria tiarella. Figs. 7 and 8. Early hydranth stages. Fig. 9. 

 Apical region of a stem, showing monopodial form of branching. The hydranth a 

 remains apical, the stem below it increases in length and the bud b becomes a lateral 

 branch like c. 



dranths. Since these early stages are enclosed in a thin perisarc 

 they are perhaps not directly comparable as regards suscepti- 

 bility with later naked stages, but in Obelia they are in general 

 less susceptible than later stages such as b and /, Fig. 10, which 

 are also enclosed in perisarc. On the other hand, they are more 

 susceptible than the stem regions from which they arise. These 



