228 HYATT, 



Ammlus varies from f to $ at the sides, and from $ to 

 | at the ends. The spines are about .233 in length, meas- 

 uring from the exterior of the annulus outward. 



The specimens found in Fresh Pond, Mass., and those 

 occurring in Pennissewassee Pond, Maine, differ in the 

 number of tentacles and spines. The former have from 

 sixty to seventy -five tentacles, and the statoblasts from 

 twelve to seventeen spines, while the latter have from 

 seventy-two to eighty-tour tentacles, and from twenty to 

 twenty-two spines. The varieties of form in the masses 

 are due wholly to the contour of the surfaces upon which 

 they grow. If these be flat the mass becomes sub-coni- 

 cal ; if around a twig, spindle-shaped ; on the end of a 

 short projecting stump of a branch, a rotund mass, as in 

 PI. 9, fig. 4. 



When the ectocyst decays, as previously remarked, in 

 old age, most of the colonies either dying or floating off 

 becomes attached and live for some time isolated, but do 

 not increase in size ; some, however, continue to live 

 more or less widely separated upon the remains of the 

 ectocyst, but in consequence of the removal of the lateral 

 pressure from surrounding colonies, lose their sub-angular 

 hexagonal form 



The polypides are found only upon the outer portions 

 of the lobes in the colonies, the inner surface being left 

 bare, spotted however with yellowish and opaque white 

 blotches, the remains of the tentacles and geimme of dead 

 polypides in different stages of absorption. 



In this process of absorption of dead polypides the 

 stomachs disappear first, the tentacles next, the gemma? 

 last. The persistence of the latter is interesting, because 

 they vanish in the living Plumatellae and Fredericellse 

 soon after 1he breeding season of early spring is passed. 

 The large size of the albuminous envelope of the winter 

 buds, very seriously incommodes freedom of motion, in 

 the muscles of living polypides, and presses the stomachs 

 out of place. The statoblasts are largest and most 

 crowded near the centre, where the polypides first die out. 

 These circumstances would imply that the growth of the 

 gelatinous covering was not only a matrix for the booklets, 

 but served in part at least to accomplish the death of 



