MUSEUM OF COMPARATIVE ZOOLOGY. 179 
anterior body region. The stomach (s) fills most of the body cavity from that 
point to the sixth segment of the posterior region, The intestine (7) is coiled 
in the posterior part of the body cavity behind the stomach. The anus, as 
before, opens dorsally. The “tail,” a median terminal appendage, is segmented 
and slightly enlarged at the distal end into a knob or button. 
The oldest larva (Fig. 11) gives no more definite information than others 
already known in regard to the genus to which it belongs.* The posterior part 
of the body of this larva is swollen, leaving the band of cilia about midway in 
its length. The preoral lobe has become more contracted, and the external 
surface of the body is covered with small papille. Another pair of pigment 
spots — the cephalic eye-spots — has been added to the two already existing. 
The cephalic appendages have elongated so that their tips extend downward to 
the vicinity of the ring of cilia, There are now ten parapodia in the anterior 
region of the body between the cephalic appendages and the band of cilia. 
The posterior portion of the body is almost hemispherical. The median anal 
appendage is greatly reduced in size, appearing as a slight projection, on either 
side of which there are similar lateral knobs. The intestine is slightly coiled, 
and lies wholly in the posterior body cavity. 
Phyllochztopterus sp. 
Plate III. 
The youngest larva (Figs. 16, 17), of this genus which we have obfained 
resembles closely a young Telepsavus. It is mesotrochal, and has a large pre- 
oral lobe, which, like that of the older form of the same figured by Claparede 
and Metschnikoff,} bears six eye-spots upon the dorsal region. These eye-spots 
consist of a pair of median and two lateral ocelli on each side. The oral lobe 
carries on its rim, just in advance of the median pair of ocelli, a flagellum, as 
in Telepsavus. The young Telepsavus has four eye-spots; the median pair 
failing even in a larva in which the tentacles have begun to form on the sides 
of the head. The youngest Phyllochetopterus, even when it has developed into 
a larva possessing six eye-spots, is still destitute of lateral cephalic tentacles. 
* Professor Verrill (Trans. Conn. Acad., Vol. IV., Pl. XVIII. Figs. 16, 17) figures 
this larva, and in MS. explanation of plates, which he has kindly sent me, refers it 
doubtfully to Spiochetopterus. His larva is a little younger than that which is here 
figured in Fig. 19. 
t Op. cit. 
} The Annelid larva (Mesotrocha seroculata) described by Johannes Miiller (Miil- 
ler’s Archiv, 1846), by Busch (Ibid., 1847), and by Max Miiller (Ibid., 1855), seems 
more closely allied to this than to the preceding (Telepsarus larva). Like the 
Phyllochcetopterus larva, it has six eye-spots and two mesial rings of cilia separated 
by a wide segment. In the figures, however, which are given by the above-men- 
tioned authors, there is no representation of a tuft of cilia (flagellum) situated on 
the preoral lobe between two of these eye-spots, as is mentioned in the larve of 
