io6 



GENERAL BIOLOGY 



another animal character. In the midst, more or less 

 hidden by the chlorophyl and by engulfed foods, is the nu- 

 cleus. Reproduction is by fission, which, also may be ob- 

 served in favorable specimens. 



FIG. . TWO shell- Ceratium is a free-swimming 

 bearing flagellates; flagellate which secretes a 



c, Ceratium, and v, & 



Peridinium. spinous shell that is probably 



a protection against the attack of some of the 

 predaceous animals of its environment (fig. 62). 

 Dinobryon is a colonial flagellate which 

 develops an urn-shaped membranous shell 

 open at the anterior end: two flagella of un- 

 equal length project from the opening; the 

 chlorophyl is distributed (fig. 63^) in two 

 elongate tracts within the body, and is somewhat 

 obscured, as in many other flagellates, by a 



yellowish pigment. 



Upon division, one of the resulting 



daughter cells slips out to the rim of the 



urn-shaped shell, and secretes for itself 



a new shell of like form, attached at the 



base within the margin of the old one. 



Repeated divisions thus give rise to 



branched colonies. These go swimming 



about in the water in a most absurd 



fashion a contradiction to all the 



mechanics of submarine navigation the 



open end forward, as it must needs be, 



owing to the position of mouth and 



flagella. 



Gonium is a colonial flagellate of Very 



different form 1 6-celled when the col- 

 ony is grown, in a flat raft, four central 



cells destitute of flagella, and twelve 



FIG. 63. A colonial 

 flagellate, Dinobry- 

 on. c, a colony; d, 

 a portion of the 

 same more enlarg- 

 ed; e, single individ- 

 ual. 



