180 BULLETIN OF THE 
The body of the youngest Phyllochetopterus is divided into a large thick 
anterior, and a smaller posterior region. The mouth opens as a triangular slit 
on the ventral side, near the anterior extremity of the former. The posterior 
extremity of the posterior region of the body bears a short median appendage. 
The mesial band of cilia thus separates the body of the larva into two regions, 
The anterior of these, which lies in advance when the Annelid is in motion, has 
a slight depression in its ventral region which marks the position of the “ gland- 
ular body” described in the larva of Telepsavus (and Spiochetopterus). The 
cesophagus, stomach, and intestine can easily be seen through the walls of the 
body. The anus opens on the dorsal side of the posterior body region, just in 
advance of the medial caudal appendage. A still older larva (Fig. 18) shows 
one in which two rows of cilia, separated from each other by a broad segment, 
are well developed. A segmentation of that part of the posterior body region 
which is behind the smaller ring of cilia, as well as the more elongated form of 
the whole larva, is to be noticed in this worm. No cephalic tentacles have yet 
formed, and the external surface of the body is still covered with small cilia. 
The globular appendage to the posterior region of the body, figured by Clapa- 
rede and Metschnikoff,* was not observed. The discovery of the youngest ot 
these two larve of Phyllochetopterus is interesting, as showing how close the 
resemblance between the youngest known Phyllochetopterus t aud the so-called 
Telepsavus larva is ; or, that the young Phyllochetopterus larva has but one ring 
of cilia between the anterior and posterior openings of the digestive canal, as 
other mesotrochal larvae. The second and smaller ring is a later addition. 
, 
Nephthys sp. 
Plate IV. 
The very little which is known of the development of Nephthys we owe for 
the most part to Claparéde and Metschnikoff.{ Larve similar to those which 
they describe, yet in different stages of growth, were raised or fished up in great 
numbers in our work. 
The youngest of these (Fig. 1) are telotrochal, and may be classed with the 
larva of Polygordius. The preoral lobe is very large, and imparts an almost 
spherical shape to the upper hemisphere of the larva. Equatorially about the 
larva there runs a ridge upon which a circle of large and powerful cilia is 
borne. The upper hemisphere or preoral lobe is rounded ; the lower more 
pointed. The whole larva has a green color, is somewhat transparent, and is 
both Telepsavus and Phyllochetopterus, by Claparéde and Metschnikoff, and in the 
present paper. 
* Op. cit. 
+ The adult Phyllochetopterus has not been recorded in our waters. (See Verrill’s 
Check List.) Chaparéde and Metschnikoff’s identification of the larva has been 
followed in my studies. 
t Op. cit. 
