186 BULLETIN OF THE 



two palpi and two pairs of tentacular cirri have also formed. The anal cirri 

 have greatly increased in length, and now resemble simple filaments. 



When such a larva is seen from the dorsal side (Fig. 4), four large circular 

 elytra can be observed above the parapodia. The setae of the lateral ap- 

 pendages of the body terminate in a short joint, as in the youngest larva, 

 which has already been described. Rudiments of a fifth pair of elytra, the next 

 to appear, can be seen just behind the most posterior of those already formed, 

 or between it and the posterior body segment. 



The body of the larva is only partially transparent, although an intestinal 

 tract is visible from the dorsal side through the elytra and dorsal body walls. 

 The parapodia are well developed, and eight in number on each side of the 

 body. Each parapodium is single, undivided, and bears a cluster of long bris- 

 tles and a long dorsal cirrus. Each seta has a terminal joint and a basal ar- 

 ticulation, which carries a small tooth, as in the younger larvae which have been 

 mentioned above. The elytra are still of diminutive size, although they cover 

 the bases of the parapodia. The point of separation between the stomach and 

 the oesophagus lies just behind and beneath the first pair of elytra. The stom- 

 ach sends oft' lateral extensions in pairs corresponding to the second, third, and 

 fourth parapodia.* 



Larva of Nereis sp. (?). 



Plate VI. 



The young of a doubtful species of Nereis bears upon the head two lateral 

 tentacles, and two short palpi, each with a basal and terminal joint, the latter 

 of which is richly ciliated. There are also upon the head three well-developed 

 tentacular cirri. The dorsal surface of the head has six eye-spots, two of which 

 are placed near the anterior dorsal rim, and four near the posterior. All are 

 widely separated from a median line. 



The body is composed of ten segments, nine of which bear pairs of setae. 

 The parapodia are very prominent. f Each parapodium has a dorsal and ven- 



* The young of an unknown Annelid (PL IV. Figs. 13, 13") is easily mistaken for 

 the youngest Lepidonotus mentioned above. Although nionotroclial it wants the par- 

 alleled rows of black pigment spots situated above (anteriorly to) and below (poste- 

 riorly to) the mesial row of cilia. This embryo is exceptional among monotrochal 

 larvae, in possessing a single caudal appendage, which is well developed before 

 lateral caudal cirri appear. The unpaired median appendage is not unlike that 

 found in the raesotrochal larvse of Chcetopterus, Telepsavus, and PhijUochatopteriis. 

 Does this larva belong to the genus Harmothoe, or is it the young of some Bryozoan ? 



t Compare tl)is larva, as well as the young Nephthrjs (PI. IV. Fig. 12), in this 

 particular, with the strange genus Tetracjlene Verr. In respect to its color, size, 

 cephalic appendages, and other particulars, the two are very different. Many 

 specimens of Tetraqlene liave been taken in our work at Newport. (See Verrill, 

 Trans. Conn. Acad , Vol. IV., PI. X:Jf V. Fig. 10.) 



An unknown pelagic worm (PI. VL Fig. 5) was found on several excursions, 



