472 



POLYZOA 



CHAP. 



protruded (Fig. 235, 1). The degenerating organs become com- 

 pacted into a rounded mass (Fig. 235, 2 and 3, b.b), known from 

 its colour as the " brown body." This structure may readily be 

 seen in a large proportion of the zooecia of transparent species. 

 In active parts of the colony the body-wall next develops an 

 internal bud-like structure (Fig. 235, 1, b), which rapidly acquires 

 the form of a new polypide (Fig. 235, 2 and 3). This takes the 

 place originally occupied by the old polypide, while the latter 

 may either remain in the zooecium in the permanent form of 



Fig. 235. Flustra papyrea Pall. Naples. x 50. Illustrating the development of a 

 new polypide after the formation of a "brown body." In 1, a, two masses formed 

 from the alimentary canal ; b, young polypide-bud ; b.b, degenerating tentacles ; 

 c, connective tissue : 2, another zooecium, later stage ; b.b, brown body ; r.m, re- 

 tractor muscles ; s, stomach ; t, tentacles of new polypide ; t.s, tentacle-sheath : 

 3, the same zooecium, 191 hours later ; letters as in 2. 1 and 2 are seen from 

 the front, 3 from the back. 1 



a " brown body," or pass to the exterior. In Flustra the young 

 polypide-bud becomes connected with the " brown body " by a 

 funiculus (Fig. 235, 1, 2). The apex of the blind pouch or 

 " caecum " of the young stomach is guided by this strand to the 

 "brown body," which it partially surrounds (3). The "brown body" 

 then breaks up, and its fragments pass into the cavity of the 

 stomach, from which they reach the exterior by means of the anus. 



There is some reason to believe 2 that these remarkable pro- 

 cesses are connected with the removal of waste nitrogenous 

 matters. The Marine Polyzoa are not known to be, in most 

 cases, provided with definite excretory organs, although it is 



] From the Quart. J. Micr. Sci. xxxiii. 1892. - Ibid. p. 123. 



