730 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [12] 



layer is differentiated into two distinct layers. The outer of these layers 

 is finely granular, and contains very few longitudinal fibers. In it the 

 radiating and circular fibers predominate. The inner layer, on the other 

 hand, is coarsely granular, and contains a considerable number of longi- 

 tudinal fibers. The outer of these two layers soon separates from the 

 other along the line of fine circular fibers to form the projecting pos- 

 terior edge of the segment. Next within the granulo-muscular layer is 

 a thin layer of circular fibers, and within this again a thick layer of 

 longitudinal fibers. The latter are very large, although not at this point 

 in distinct fasciculi. Farther back towards the posterior end they be- 

 come fascicled. The connective tissue in this layer appears finely granu- 

 lar in transverse sections, while in longitudinal sections it appears as a 

 network of delicate fibers which fills up all the interstices between the 

 longitudinal fibers. The longitudinal fibers of the inner j)art of the 

 granular layer do not differ essentially from those of the longitudinal 

 muscle layer proper, except that they are more scattered, while their 

 interstices are filled with connective tissue in which are numbers of 

 both coarse and fine granules, highly colored in carmine-stained sec- 

 tions. The longitudinal muscular fibers in general do not lie parallel 

 with each other. They form, indeed, a maze of interlacing and appar- 

 ently anastomosing fibers whose general direction is longitudinal. The 

 diameter of the largest single longitudinal fibers in the granular layer 

 is about .004 nnu , aud, in the longitudinal muscle layer proper, twice as 

 much. The longitudinal muscle layer is separated from the inner core 

 of the segment by a thin layer of circular fibers. It is, moreover, inter- 

 rupted at the margins where it is penetrated by the margins of the 

 inner core. The latter is fusiform in transverse section, and contains 

 the reproductive organs. It is crossed by numerous fine transverse con- 

 nective fibers, and extends nearly to the margins of the segment, where 

 it appears to be continuous with the inner granular layer. It is quite 

 narrow except in ripe segments, where the center becomes very much 

 enlarged on account of the presence of the numerous ova. The central 

 mass of ova enlarges at the expense of the longitudinal muscle layer. 

 The walls of the segment are also bulged outward by the mass of ova. 

 The reproductive apertures are near the median line on one of the 

 lateral sides. They are very close together and rather small. Each 

 aperture represents a pair of sexual organs, cirrus and vagina. Upon 

 making a few longitudinal sections on the lateral face which bears the 

 reproductive apertures, the small vaginal opening comes into view. 

 It opens into the common aperture from behind and near the surface. 

 The larger aperture continues into the cirrus-bulb, which has thick mus- 

 cular walls composed of circular fibers. The cirrus was retracted in all 

 cases. It is about .008 mm in diameter. The bulb is rather long and 

 descends into the segment vertically nearly to the middle. The rela- 

 tive position of the various organs was not ascertained with entire sat- 

 isfaction. The vagina, however, lies close to the posterior side of the 



