204 HYATT, 



TEEDEKIOELLA. 



These are plant-like animals with graceful dendritic 

 forms, common in our brooks and ponds (PI. 7). They 

 cling, immovably fastened by their ectocyst, to the lower 

 surfaces of submerged stones, or floating boards ; and 

 thrive best in the darkest places, often carpeting the dismal 

 recesses, under the loosened bark of dead branches, with 

 their lovely, campanulate corollas. 



Nothing can exceed the exquisite beauty of these small 

 "phytozoons"; their symmetrical outlines, the alertness of 

 the motions of the polypides, and the surprising complexi- 

 ty of the internal structure of their transparent bodies rich- 

 ly repay the labors of the microscopist. 



Coencecium. This part of the colony, formed by the tu- 

 bular dark brown trunk and branches, is made up of lines 

 of little hollow twigs, or cells, each separate cell encasing 

 a single polypide, and opening into the preceding cell, or 

 parent Polyzoon, at the lower end. Thence the cells 

 are generally attached for some distance to the surface, al- 

 though frequently the entire branch is free, the lowest cell 

 alone being attached. The extremities of the cells bend 

 upwards, and are always free, but vary exceedingly in 

 length. The color is due to the ectocyst, which is a thin 

 gelatinous excretion, soft, and transparent when first de- 

 posited, but acquiring with age a dark brown hue and 

 parchment like consistency (PI. 7, figs. 4, 5, D). This ex- 

 cretion is the product of the coencecial endocyst, or true 

 body wall of the branches and polypides (PL 7, figs. 4, 5, 

 6, E). The endocyst is continuous throughout the gener- 

 al system of branches or coenoecium, and the latter may, 

 therefore, be regarded as a common tubular cavity, more 

 or less cut up into cells. Some scattered, partial divisions, 

 made by ring-like folds of the endocyst, open in the centre, 

 are found in each colony, but these are not constant, and 

 occur only at rare intervals in the branches.* 



Polypide. The free portions of the cells are capped by 

 translucent tubes crowned with thread like tentacles radia- 

 ting from the periphery of the Lophophore, or floor of the 



*Siinilar to those of Plumatella. PL 8, fig. 6. 



