MUSEUM OF CO:\IPARATIVE ZOOLOGY. 197 



The intestine is more globular in shape than the oesophagus, opening internally 

 into the stomach, and externally through the anus. Its inuer walls are cil- 

 iated, and its cavity is partially tilled in many specimens with feces. 



In a second slightly older larva (Fig. 11) of Polygordius, several additions in 

 structure have been made, and marked modifications in form have taken place. 

 In J he general outline, the most important change is the flattening of the whole 

 larva, especially on the lower hemisphere, by which the e(|uatorial axis is rel- 

 atively very much increased. The flagellum on the apex of the upper hemi- 

 sphere has disappeared, and the two ocelli have drawn still more closely 

 together; so that both now lie very close to the apical pole. The stomach 

 has become more elongated in shape, while the oesophagus has assumed a more 

 tubular form. The begiuuings of the funnel-shaped bodies described by 

 Hatschek in the European Loven's larva can be seen as two globular sacs (< ), 

 one on each side of the stomach, on a level just above a plane passing through 

 the equatorial ring of cilia. Two prominent fibres arise from the collection of 

 cells upon which the ocelli are placed, and jjass to the lips above the mouth. 

 Two other threads have a similar origin, and extend meridionally on each 

 side of the stomach to the clusters of cells on the inner walls of the lower 

 hemisphere, at the anal pole of the body. A third pair of threads, hitherto 

 unnoticed, take their rise from the same clusters of cells at the anal pole, and 

 extend parallel with each other to the lower lips of the mouth. They end 

 near two pigment bodies which are constantly found in this region. 



The different larval stages m the development of Loven's larva which lie 

 between that represented in Fig. 11 and the adult Fig. 18 have been figured by 

 Hatschek for the European species, and for the American representative by 

 A. Agassiz. New figures of the American larva are introduced in order to 

 show the pecuHar brown bodies found about the bell margin, which seem to 

 be characteristic, and the two ventral " nerve cords " shown in Fig. 14, v n, 

 which are unrepresented in any drawings of these larvae which have been pub- 

 lished. With the exception of these two differences, our common Loven's larva 

 is similar to the European. 



Capitella (young). 



A larva referred to the genus Capitella has been taken several times in our 

 Newport fishing. These were always in the same condition as that figured in 

 Plate III. Figs. 19, 20, and do not differ essentially from one already repre- 

 sented by Claparede and Metschnikoff.* 



Lumbriconereis. 



Plate VII. 



The cove near the laboratory is the home of many genera of Annelides which 

 live in the fine mud covering the bottom in many places. In the months of 

 June, July, and August, a plentiful supply of eggs in all stages of growth, 



* Op. cit. 



