330 ; PROTULA. 
coral reefs. In some arborescent corals nearly every branch is hollow and contains a Serpulid 
over the ordinary tube round which the coral polyps have spread and enclosed it. Yet even 
in Britain the rocks and stones near low water on both eastern, and especially the western, 
shores, are covered in many cases with the white tubes of Pomatocerus, and many stones 
and shells from deep water are similarly coated with Hydroides or other form. Moreover, 
the vast number of the Spirorbids on stones, the blades of Fucz, and the stems and branches 
of corallines inshore and off shore still further extend their distribution. 
The Serpulids are a very old group, ranging from the Silurian rocks upward, some, 
such as Serpula, occurring in the Upper Silurian, Devonian, and Carboniferous formations, 
Spirorbis again extending from the Upper Silurian to modern times. Recent remarks on 
some of the genera have been made by F. Chapman! and other authors. 
An interesting point in the development of the Polychzets is the fate of the vitelline 
membrane. Not a few authors, such as Barrois, Malaquin, Salensky, Wilson, ‘Drasche, 
Treadwell, Claparede, Mecznikow and others hold that it becomes the cuticle of the larva. 
Others, again, such as Vignier for Grubea, Gotte for Nereis, Drasche for Sabellarva, Wilson 
for Chetopterus, and Hisig and Pierrantoni for Capitella and Saccocirrus state that it 
disappears. In the present group Claparéde and Mecznikow state that it disappears in 
Spirorbis, Fabricia and Dasychone, Salensky observed it disappear in P2leolaria, Gotte mm 
Spirorbis, Hatschek in Hupomatus, Roule in Dasychone. Stossich, on the other hand, 
insists that it forms the cuticle in Hupomatus, and Conn in Serpula uncinata and S. glomerata. 
A recent research by Soulier® demonstrates that the vitelline membrane in Serpula crater 
and Protula gradually disappears during development, splitting at the posterior end and 
then vanishing in front. The same author’ (Soulier) goes minutely into the fifth stage of 
segmentation (thirty-two cell-stage) of Protula meilhaci after the manner of the American 
authors, showing the origin of the various blastomeres (micromeres and macromeres), 
and in a subsequent paper* treating of further stages—cross and rosette. He thinks that 
the differences between the development of Protula and Nereis and Capitella are only 
secondary. 
Genus CLXXVI.—Protuna, Risso, 1826. 
Protula, Risso, ‘1/Europa mérid., p. 405; Protula, Blainville, Milne Edwards and 
Grube: Sabella, Cuvier, ‘Réeg. Anim.,’ ii, 1830, p. 192; Apomatus, Psygmobranchus, 
Philippi, Wieg, ‘ Archiv,’ 1844, p. 189; ‘Ann. Nat. Hist.,’ xiv, pp. 155.and 156; Terebella, 
Blainville, ‘ Dict. Sc.,’ t. Iv, p. 435. 
Cephalic region truncate, with a free collar, the edge of which is continuous. Branchive 
plumose and fan-shaped, the filaments united in a tough base, occasionally spiral. Tentacles 
two. Body elongate and tapering posteriorly; the anterior region of eight segments with a 
lateral membrane on each side equal to the diameter of the body, supported by a greatly 
developed dorsal process of the foot. Posterior region tapering to a terminal anus. 
1 «Journ. Roy. Soc. Victoria,’ xxx1, p. Ld. 
2 «Arch, Zool. Hxpér.,’ t. lvi, No. 1, p. 16, text-figs. 1—38, 1916. 
5 Ibid., No. 4, p. 100. 
4 Thid., t. lvii, No. 1, p. 14 (1918). 
