182 BULLETIN OF THE 



on, and new segments have been interposed between the ciliated ridge and the 

 anal pole. A pair of pigment spots (k) resembling ocelli, or " eye-dots," appear 

 in the dorsal walls of the prteoral lobe. The general appearance of this larva 

 from the ventral side is characteristic. The prajoral lobe is no longer hemi- 

 spherical, but the elevation of the pole and the formation of a circular ridge or 

 zone a short distance above the ciliated equator imparts to it a characteristic 

 shape. The rounded projection or polar elevation of the pra;oral lobe above 

 this zone is crowned by a cluster or tuft of cilia. A black spot is found 

 on each side of a median dorsal line passing to the apex of this protuberance. 

 The green zone which was formed in the cephalic region of Fig. 2, while the 

 prseoral lobe had a regular hemispherical shape, has now increased in width, 

 and the wall in which it lies bulges out, forming a collar about the lol)e. 

 This collar has a more greenish color than the rest of the larva. About its 

 lower rim, however, there is considerable black and some red pigment. The 

 mouth lies near the equator, situated similarly to that of the young Pobjgordius 

 (" Loven's larva "), between two rows of cilia. 



The most important change which results in passing from that represented 

 in Fig. 4 into the next oldest Ncphthijs (Fig. 5) is a still further elongation of 

 the body, and consequent diminution in size of the praeoral lobe. The most 

 important addition is the formation of the parapodia, the spines (Fig. 6, b) of 

 which even in this early stage are serrated, like those of the known species 

 of Nephthys. The number of body segments is nine. Each parapodium (Fig. 

 12, 6) has a dorsal and ventral cirrus, and bears two bundles of setae, each 

 composed of several short, serrated spines. The form of the stomach and 

 intestine is more elongated than in the earlier larvae. 



A larva a little older (Fig. 6) than that last described, although not unlike it 

 in general contour, differs considerably from it in some particulars. This dif- 

 ference is a result of changes which have taken place in the internal organs. 

 On looking at the larva from the ventral side, the mouth can be seen just 

 below the equatorial ring of cilia. Behind the mouth through the body walls 

 appears the cEsophagus, which when seen from the ventral side has a circular 

 profile. Below the mouth, extending to the region of the seventh body seg- 

 ment, is the stomach. At this point (seventh segment) the intestine begins, 

 and from it is continued into the terminal body segment. Just below the 

 junction of the cEsophagus and stomach, on the right-hand side of the figure 

 representing a larva of this age seen from the ventral side, there will be no- 

 ticed an indentation in the stomach walls, forming by the enlargement a space 

 in the body cavity, in which lies a globular sac. The pulsations of the sac in 

 this and subsequent larvae can be plainly seen through the body walls. The 

 terminal body segment ends bluntly in two lateral prominences, which are 

 colored green. In the median line between them on the dorsal side there is a 

 small unpaired appendage, which persists in subsequent stages into the oldest 

 larva of Nephthys which was studied. 



Fig. 7 represents a larva of Nephfhijs still older than the last. The whole 

 larva, more especially the body region below the circle of cilia, has become 



