458 Report of the State Gteologist. 



distance of the lophophore, they separate from it, and continuing 

 to the right and left, are inserted one in each arm of the lopho- 

 phore. Their action is to rotate the tentacular crown and to 

 depress the lobes (fig. 24, p). Yan Benedbn first directed atten- 

 tion to a set of parallel bands running along the margin of the 

 lophophore. These bands are continuous with one another 

 below, but when they arrive at the space between adjacent 

 tentacles, each band divides in two, apparently running up 

 opposite sides of adjacent tentacles. 



These bands do not present any fibroid structure. Yan 

 Beneden considered them muscles, and that to their action was 

 due the movement of the tentacles. They have not been ob- 

 served in the Gymn )L(emata, but if they are muscles and the 

 movements of the tentacles are due to them, they will probably 

 be found in all Brtozoa. There is another set of muscles 

 peculiar to the Hippocrepian forms, which consists of a circle of 

 short, stout radiating fibers (fig. 22, ^, ^, and fig. 24, o^ r). They 

 take their origin on the inner surface of the endocyst, on the 

 same plane, and are inserted in the tentacular sheath some dis- 

 tance below the mouth of the cell, on a plane parallel to that of 

 their origin. Their action is to prevent the eversion of the 

 whole of the tentacular sheath, and to keep the mouth of the 

 animal at the proper distance from the cell aperture. 



Mr. Ha-ncock says in relation to this muscle: "The true value 

 of these muscles will be understood if we refer to the marine 

 genus B0WEKBA.NKIA, in which they are deficient, and of course 

 the tentacular sheath can be wholly everted, and accordingly the 

 animal can reach to a greater ' distance than it could otherwise 

 have done, but an apparatus of extraordinary beauty is provided 

 to obviate the inconvenience that must have arisen from the 

 greater elevation of the tentacular disc above the support of the 

 horny cell. This is effected by what may be considered an 

 elongation upward of the cell. Numerous setae, bound together 

 by a membrane, are attached to the lips of the orifice of the cell, 

 so that when the polyp is exserted they stand up in a circle, sur- 

 rounding the lower portion of the exposed part of the animal 

 (fig. 25, d\ and give support to it. By this means the far out- 

 stretched tentacular disc is brought completely under the control 

 of the muscles for directing its movements. 



