954 



FRESH-WATER BIOLOGY 



13 (10) Horizontal branches only. Cuticula delicate, colorless, hyaline. 



Elevated aperture-cone wrinkled and besprinkled with 

 white. Free statoblasts nearly circular. 



Plumatella punctata Hancock 1850. 

 Stock repent and open, 

 forming long hyaline tubes 

 that give rise to only a few, 

 likewise repent, lateral 

 tubes. . . . Var. a, prostrata. 

 From Maine, Pennsylvania, 

 Illinois, and Lake Erie. 



Stock repent, very thickly 

 branched, completely cover- 

 ing the substratum, which 

 seems enveloped in thick 

 layer of gelatinous vesicles. 

 Var. /3, densa. 



Fig. 1400. Plumatella punctata, 

 var. a. (a) Colony two-thirds 

 natural size, (b) Branch much 

 magnified. (c) Statoblast. 

 X 40. (After Kraepelin.) 



14 (7) Statoblasts large, elliptical, but at each end drawn out into a sharp apex ; 



broad float, hooks absent. Lophopiis cristallinus Pallas 1766. 

 Colony shaped like a sack; erect, sometimes more or less lobed by indentations of margin, 

 looking then sometimes hke a glove. Outer cuticula layer delicate and hyaline, more incrusted 

 at base. Polypides scattered, a group of them rising from each lobe. Lophophores with about 

 60 tentacles. The colony may divide along the constrictions between the lobes. Habitat, 

 chiefly standing water, such as pools, or, rarely, slowly flowing water. Chiefly attached to 

 plant stems. From Schuylkill and Illinois rivers. 



15 (7) Statoblasts with hooks 16 



16 (17) Colonies hyahne, in the form of a rosette, lobed, with horizontal 



tubes only Pectinatella Leidy . . 17 



They secrete a great gelatinous base which is common to many colonies. Aperture slightly 

 elevated above common coenecium. Statoblasts large and circular to subrectangular, with 

 broad bent float and one marginal row of anchor-shaped hooks. 



1 7 Pol)^ides scattered or in double row along each lobe , the gelatinous base often 



10 to 20 centimeters thick. Pectinatella magnifica Leidy 1851. 



Tentacles 60 to 84 in number. Statoblasts about i mm. in diameter, provided with 11 to 22 



hooks from 0.15 to 0.25 mm. long. Habitat, submerged branches or twigs of trees, wooden 



stakes, gates of dams, walls of reservoirs or stones in brooks. Shady situations, such as south 



walls of reservoirs, or wood-covered streams. From Maine to Mississippi. 



Fig. 1401. Pectinatella magnifica. (a) Young colony, natural size, (b) Section highly magnified, (c) 

 Statoblast, ventral view, (d) Statoblast in profile. X iS- (e) Colony on plant stem. X |. (After Kraepelin.) 



