514 TRANSACTIONS OF SECTION D. 
those already formed backwards, so that the most posterior stolons are the 
oldest... Typigally ectoderm and mesoderm alone take part in the formation ‘of 
the stolons; which thus differ from those of all other Syllids in the entire 
absence of an alimentary canal, though otherwise completely developed. 
In T'rypanosyllis gemmipara from the N.W. Pacific stolon-formation is 
accompanied by the rapid addition to the stock of a tail of forty to fifty seg- 
ments. This, unlike the stolons, contains a direct prolongation of the alimentary 
canal of the stock, but, like them, develops generative products. In one case 
this structure actually developed a head with eyes-and tentacles, and separated 
off as an individualised stolon, differing from the others only in its complete 
alimentary canal. In 7'rypanosyllis Crosslandi from Zanzibar stolon-formation is 
unaccompanied by posterior regeneration of the stock, but there is, at least 
occasionally, an ingrowth of endoderm from the ventral lip of the anus, into the 
dorsalmost stolon of the group. 
At the beginning of proliferation a cushion of mesoblast arises ccvered 
by a thickened layer of ectoblast. Each stolon is a centre of proliferation, and 
the lines of separation are occupied by -non-proliferating epithelium. The 
cushion is formed by a mass of connective tissue and muscle-fibres in which 
occur vast numbers of rounded cells with deeply staining nuclei, often dividing, 
which enter the interior of the stolons as they form. In the earliest stage of 
proliferation observed (7'. Crosslandi) the body cavity near the region of pro- 
liferation was almost filled by leucocytes, which also migrated into the solid 
cushion. It is suggested that they partly serve a nutritive function but also 
give rise to the greater number of the mesoblast cells. The mesoblast does not 
appear to reinforce the proliferating ectoblast. : 
From the mesoblast of the cushion are formed the gonads, the coelomic 
epithelium, and the connective tissue, but the muscles of the stolons are directly 
developed from the longitudinal muscles of the stock, bundles of which may be 
traced radiating through the cushion of proliferation and entering the stolons. 
Blood-vessels, it must be noted, are entirely absent. From the ectoblast are 
developed the usual ectodermal structures, with the exception of the nervous 
system, which is formed directly by branches from the ventral nerve cord of 
the stock growing into the stolons. 
3. On a Budding and Hermaphrodite Annelid (Filograna implexa, 
Berkley). By Professor W. C. McIntosu, F.R.S. 
This annelid has long attracted attention from the coral-like masses formed 
by its agglutinated and slender calcareous tubes, and the symmetry and beauty 
of the contained animals—which belong to the serpulids. Various species have 
been described by different naturalists, but the’ chief interest lately has been 
the very close structural resemblances between the two conspicuous genera—viz., 
Filograna, which has an operculum or lid to its tube, and Salmacina, which has 
none. The views of Berkeley, Huxley, Claparéde, Keferstein, De Quatrefages, 
Dalzell, Langenhans, Caius, Ehlers, De St. Joseph, Malaquin, and others were 
considered, and the author’s interpretation of the structure of the two groups 
(with, the aid of large diagrams) was given, and after the examination of many 
examples from the British and other seas, the points of distinction between 
the two groups were severally dealt with, and it was shown that the presence or 
absence of an operculum on the branchial stems was not a point’ on which great 
dependence could be placed, since in the North—for example, in Shetland, the 
Moray Firth, and St, Andrews Bay—amidst vast swarms of those devoid of 
opercula a few occurred with them. Further, it was shown that these organs 
(opercula) in this form are exceedingly variable in development, and that where 
they are absent the tips of the branchial filaments show great susceptibility to 
growths of a more or less conspicuous character, the largest processes occurring 
in the Neapolitan form—in which their outline is elongate-ovoid. Variability is 
not confined to the tips of the filaments, for the pinnz are short, long, or of 
medium length, according to the age or surroundings of the example. The 
- bristle-tufts of the anterior region likewise vary from five to ten pairs, yet 
throughout the whole series of those with and those without opercula the 
