No. 424.] THE GENUS TRYPANOSYLLIS. 311 
GENERAL CONSIDERATIONS. 
From the standpoint of comparative morphology, the col- 
lateral buds of Trypanosyllis may be regarded as structures 
of the same order as the stolons of Autolytus or Myrianida, 
but with the important difference that the buds in this case 
are lateral outgrowths, whereas in stolonization they are the 
result of linear growth and differentiation. As stolons, they 
extend the organic axis of the parent, and the alimentary canal 
passes through them all, to terminate at the anus located in 
the pygidium of the oldest stolon. 
At first thought it would seem as though the buds of 
Trypanosyllis are more appropriately comparable to the sexual 
zooids of Syllis ramosa. The superficial resemblance to the 
latter is indeed striking. In both instances we have a lateral 
outgrowth of the stock, to which it is attached at the head end 
by a pedicle; in both, the zooids are the bearers of the sexual 
products (which do not develop in the stock), and both have an 
imperfectly developed prostomium bearing highly developed 
eyes. There are, however, two important points of difference: 
(1) the pedicle of the sexual zooid of Sy//is ramosa is segmented, 
and the segments even bear rudimentary cirri!; (2) the sexual 
zooids as well as the asexual branches of SS. ramosa contain a 
branch of the alimentary canal, fully continuous with that of 
the stock. In neither of these respects does the sexual bud 
of T. gemmipara in the least resemble the sexual bud of 
S. ramosa. The sexual zooids of the latter species are evi- 
dently specialized, fructifying branches of a widely branching 
asexual stock. They are equipped with large eyes and special 
swimming organs (natatory setze), and break away from the 
parent stock at maturity. In all these respects they differ, 
it is true, from the purely vegetative branches, but these 
differences are merely adaptive to the special functions of 
insuring fertilization of the eggs and disseminating the species. 
aether the somite or somites from which the sexual buds 
of Trypanosyllis arise is to be regarded as homologous with 
the others cannot be decided from the material at hand. No 
1M’Intosh. Challenger Reports, vol. xii (1887), Pl. XXXIII, Fig. 11. 
