254 



AQUATIC MICROSCOPY FOR BEGINNERS. 



rows of doubly barbed hooks, whose purpose, I imag- 

 ine, may be to prevent the statoblast from being 

 swept away by the currents, since the hooks form 

 most effectual anchors. These marginal spines' or 



Fig. 176. — Statoblast of Pec- 

 tinatella. A, annuius. 



Fig. 177. — Front and side views of Stato- 

 blast of Cristatella. A, annuius. 



double hooks are visible with a good pocket-lens, but 

 on the majority, there is a structure demanding the 

 compound instrument for its elucidation. This is the 

 annuius, a brown ring encircling the body of the stato- 

 blast and composed of innumerable hexagonal cells. 

 It occurs on all known forms except on those of a 

 single genus, Fredericella (Fig. 173), where the winter 

 eggs are entirely smooth. 



Within the body of each Polyzoan is a cord-like 

 structure extending from the lower end of the stomach 

 to the base of the cell-like posterior part of the ani- 

 mal. This is named the funiculus, and from it the 

 statoblasts are formed by a process of budding. 

 '■They arise, " says Professor Alpheus Hyatt, "within 

 bud-like swellings of the funiculus, and, enlarging, 

 slowly push out to the surface of the cord, and up- 

 wards toward the stomach, until finally they hang upon 



