172 BULLETIN OF THE 
the cavity as formerly, and its course is more tortuous, especially in the pos- 
terior region of the body, than in the preceding. Not only have the temporary 
cephalic bristles fallen off, but also the long spines found on the body have 
been replaced by shorter and less conspicuous seta. The most persistent of 
these deciduous spines are situated in the middle region of the body. In this 
larva, however, these have given place to minute bristles, and to the “ crochet 
hooks” (Fig. 13, 6) of the terminal region. I am inclined to think that the 
temporary body bristles are confined to that portion of the body which is 
described above (Fig. 1, ar) as the anterior region. 
The colors of the oldest larva (Fig. 13) are similar to those of the younger. 
The preoral lobe has little color except in the green regions near the eye- 
spots. There is in the cephalic dorsal walls, in front of each of the lateral 
eye-spots, a hemispherical green body. Just below and in advance of the 
median pair of eye-spots there is a body of the same kind, which has a median 
prolongation extending nearly to the anterior margin of the preoral lobe. 
The cephalic tentacles are reddish in color. The lateral lobes on the head, 
from which the spines formerly arose, are likewise red. The body of the worm 
is green and brown, with red pigment spots.* 
The temporary cephalic tentacles are homologous with the dorsal cirri, while 
the temporary setze are strictly the same as those found on the segments of the 
body. 
It will later be seen, in a description of the young (Nerine) Spio, which like- 
wise has embryonic spines on the head, that two long dorsal cephalic append- 
ages or tentacles also exist in this genus. Here likewise these bodies may be 
regarded as homologous with dorsal cirri, and as belonging to the same segment 
as the embryonic cephalic spines, which are later dropped. The median and 
lateral antenne and the palpi are not represented in Prionospio. From this 
absence of the appendages last mentioned, we are not to suppose that they 
indicate in Lepidonotus a larger number of cephalic segments than that which 
exists in Prionospio. 
In the account given above, the two long appendages to the head are called 
tentacles, from the fact that in younger larve they resemble so closely the 
tentacles of other Annelides, especially those of the Spionide. In function, 
however, they are probably in later larvee branchie, and ultimately assume a 
form approximating that of the branchiz in other Annelides. In the growth 
of the worm, additional branchie must also be formed, if we are right in our 
reference of this larva to Prionospio. Intermediate larvee between that last 
mentioned and the adult may show that a new identification must be made, 
and that the larve do not belong to Prionospio. 
* Professor Verrill has kindly examined some of my sketches of this worm, and 
writes me that they can perhaps be referred to the Annelid which he has mentioned 
in Amer. Jour., November, 1882, under the name of Prionospio. (See also Trans. 
Conn. Acad., Vol. [V., Pl. XX VII. Fig. 3.) 
ee a ee 
