628 EDWARD POTTS. 



Body soft (hydra-like), with but slight power of extension or 

 retraction; without tentacles or cilia, but terminated by 

 conspicuous symmetrical capitula varying from time to time 

 from a generally hemispherical shape, and bearing upon or 

 near their surfaces fifty or more nematocysts, each with 

 slightly protruding palpocils. At the extremity of each 

 capitulum an oval aperture, expansible and contractile, was 

 with difficulty determinable, but was finally abundantly 

 proven (fig. 19, PI. 36). 



The creature was fixed in position, and apparently without 

 power of locomotion when once attached — standing or swa}'- 

 ing upon its proximal extremity, which latter was specialised, 

 as in the common Hydra, into a pedal disc or foot (fig. 20). 

 Besides the nematocysts collected within the limits of the 

 capitulum, others were rather sparsely distributed throughout 

 all parts of the ectoderm. 



The animal was often entirely quiescent ; at other times 

 its sole movement consisted in a very deliberate writhing or 

 swaying of the whole body, or a curving of the capitulum 

 abruptly against the body as a bent finger curves upon 

 itself. 



During the fifteen weeks or thereabouts that these crea- 

 tures were under close daily and nightly observation, at least 

 fifteen individuals, old and young, were seen; and as the 

 positions of the mature forms seemed unchangeable, and the 

 larva) had but slight — or even accidental — powers of loco- 

 motion, there was little difficulty in identifying them from 

 day to day. It must be observed, however, that on account 

 of the scarcity of specimens, and the apparent impossibility 

 of removing any from its place of attachment (on rough 

 stones) without fatal result, I was unable to place them in 

 good positions for examination by transmitted light, and 

 that, standing as they generally did, upon opaque surfaces, 

 and in positions directed more or less toward the observer, 

 their internal structure, and the changes occurring therein, 

 could not be seen with entire success in the living animal. For 

 ijistance, notwithstanding the most careful watching during 



