194 “BULLETIN OF THE 
passes to the dorsal flexure from the internal end of the esophagus, is fully 
formed before any trace of the anal ring of cilia or the lateral bodies (“ lap- 
pets ”) found near the stomach have appeared. 
The second of the two figures of Tornaria (Fig. 17) is taken from a larva 
still older than the last, from which it differs in one or two particulars. The 
most important character which has been acquired in the growth of the former 
is a belt of cilia not far removed from the anal pole, which is found in all later 
stages in the development of the worm up to its metamorphosis into Balano- 
glossus. The same ciliated belt we also find in the larva P. recurvatum, the 
young of the Nemertean worm which we have studied, but it does not exist 
in the known species of Pilidiwm, which are the nearest allies of our new 
Nemertean larva. It is, however, represented in Actinotrocha. 
A noticeable fact is that the lateral bodies found near the stomach in older 
Tornarie have also not yet appeared in the growth of the internal organs at 
this stage of development. 
There is another difference between the second and the first of these two 
larval youngest stages of Tornaria, On either side of the cesophagus, originat- 
ing from the inner end of the muscular thread which arises from the eye-spots 
at the apex of the larva, is found a pair of rein-like bodies in the form of 
threads, which extend to points on either side of the mouth. It is not known 
what their function is, but their position is the same as that of like threads 
which have been described elsewhere in this paper, for the first time, in our 
common Loven’s larva, similar to its European representative, referred by 
Schneider and Hatschek to the strange genus Polygordius. There is also an- 
other characteristic in the very young Loven’s larva never yet observed by 
others, which seems to me of some importance in theoretical questions con- 
cerning the affinities of Polygordius. A very young Loven’s larva was found, in 
which a long vibratile cilium is borne upon the apex, just as has been mentioned 
in Pilidiwm and the larva of the above-described Nemertean. Moreover, this 
cilium, which has the character of a flagellum as far as size goes, rises from a 
specialized portion of the body of the larva upon which eye-spots are borne. 
The flagellum in Loven’s larva is an embryonic structure, and the portion of 
the larva which carries it is directly changed into the head of the future worm. 
In the Nemerteans, however, the flagellum is embryonic, like that of Loven’s 
larva, but the body of the larva plays no part in the formation of the head of 
the worm, but by its wonderful metamorphosis makes the whole posterior 
extremity of the larva. No Tornaria has been observed with this flagellum 
at its apex, unless we homologize with it a small tuft of cilia larger than 
the others on the surface of the body, found at the apex of our youngest larva. 
Close as the resemblances between Tornaria and Pilidium recurvatum are, 
there are many very intimate relationships between the latter and the young 
of the Gephyrean worm Phoronis when known as Actinotrocha. The rapidity 
of the transformation of the Pilidium into the Nemertean, more especially the 
apparent evisceration and turning inside out of the larva at that time, led me 
at first to regard my larva as the young of some unknown worm allied to 
