334 NEREIS (ALITTA) VIRENS. 



J. T. Cunningham 1 describes the segmental organ as a somewhat spherical mass 

 composed apparently of a convoluted tube ending in an efferent duct which opens on the 

 ventral surface. The internal aperture is funnel-shaped and fimbriated and seems to 

 open on the anterior face of the septum. He thinks the generative elements are not 

 discharged through this organ, but by dehiscence through the body-wall. 



Reproduction.— In those procured in May the females discharged from the broken 

 surfaces (posterior) a cloud of grass-green ova. They measured from -^ to T -^ 5 - - of 

 an inch (O03 - 0'02 mm.), and contained numerous granules that by transmitted light 

 have a pale brownish or greenish aspect, the larger masses especially showing the former 

 tint. On the bottom of the vessel the ova formed a deep grass-green layer. The addition 

 of acetic acid did not affect their colour. 



The males when placed in spirit about the end of April (21st) emitted streams of 

 spermatozoa from the bases of the feet. In the fresh specimen the sperms maintain 

 an active wriggling motion. Amongst these are also some bodies longer than the head 

 of the ordinary form, and even more active in movement. The masses of sperms in the 

 ccelom assumed a greyish hue. 



The digestive apparatus and the whole organs of the animal at this season (April 

 and May) seem to be modified for the furtherance of reproduction. 



In October the small ova occur in masses at the bases of the feet, extending into the 

 lamellae. To the naked eye they are pale, but under the microscope slightly greenish. 

 Moreover, in the bottom tow-nets toward the end of the month numerous faintly yellow 

 or greenish-yellow larvas in the trochophore stages are found, with a diameter of about 

 •228 mm. At the same period an early mesotroch stage is met with. Neither tentacular 

 cirri nor eyes are present, and the snout is short, whilst only traces of the feet in the 

 form of lateral papillge are observed. A little pinkish-white pigment occurs at the 

 ciliated ring. The next stage presents three bristled feet on each side, though neither 

 eyes nor tentacular cirri are present. Two short tentacles spring from the anterior 

 border of the snout, and two rounded anal cirri occur posteriorly. 



Toward the end of October a considerable number of a later stage appeared in the 

 bottom-net, and they were readily recognized by the pale pink pigment in the form of a 

 ring behind the preoral belt of cilia, and also by similar pigment posteriorly on each side 

 of the purplish streak of the alimentary canal (Plate L, fig. 12). The pigment on the 

 head forms a flattened horseshoe, thus readily distinguishing this form, and there are two 

 large eyes, besides two short tentacles, which seem to spring from the ventral edge of the 

 snout, and traces of another process on each side. The preoral ring of cilia is powerful, 

 and seems to be the chief locomotor apparatus. Behind it three long cirri project — 

 probably the representatives of the tentacular cirri, which in somewhat younger stages 

 are considerably shorter. Fourteen or fifteen feet are present, each having a prominent 

 dorsal and a long ventral lobule with a cirrus. Simple bristles occur dorsally. Posteriorly 

 the pygidium has two processes like flattened papillse, probably the precursors of the anal 

 cirri, and the region has rose-pink pigment. In swimming the tentacular cirri behind the 

 preoral ring of cilia are closely adpressed to the body. 



An older stage, of the same date (Plate L, fig. 13), having sixteen bristled segments 

 1 ' Quart. Journ. Micros. Sci./ N.S., vol. 28, p. 256, PI. xviii, figs. 15 and 16, 1888. 



