Beu: Evolution of Janthina and Reduzia 
133 
Figure 8. Bubble formation by Janthina ; a sequence of schematic drawings of extension and contraction of the 
propodium, forming a bubble and adding it to the float; dorsal view. Presumably based on Janthina janthina ; copy 
at published size of Fraenkel (1927: fig. 4); magnification unknown. 
them against it while the mucus hardens (e.g., Forskal, 
1775: 127-128; Bose, 1802; Peron & Lesueur, 1807; Cuvier, 
1808; most clearly by Coates, 1825, 1828; Eschscholtz, 
1825: column 737; Quoy & Gaimard, 1825, 1832, vol. 1: 
242; atlas, pi. 29, figs 1-8; Lesson, 1826; Rang, 1829: 196, 
pi. 5, fig. 3 [showing the shell of the brooding species J. 
janthina with egg capsules beneath the float, an impossible 
combination copied in several later manuals, e.g., Fischer, 
1885: 774]; Grant, 1834; Lund, 1834a: 110, pi. 6, figs 23-26; 
Lund, 1834b; Bennett, 1834, 1840: 295-298; Costa, 1841; 
Delle Chiaje, 1841; Deshayes, 1843: 2-3; H. Adams & A. 
Adams, 1854: 86, pi. 69, figs 1-la; Benson, 1860; Adams, 
1862;Lacaze-Duthiers, 1865,1866; Jeffreys, 1867:174—189; 
Bouvier, 1886a, b, 1889; Simroth, 1895; Pruvot-Fol, 1925; 
Fraenkel, 1927; Thiele, 1929: 224-225; Laursen, 1953; 
Wilson & Wilson, 1956: 300; Okutani, 1956: text-figs 1-8; 
Fretter & Graham, 1962: 561-563; Bayer, 1963; Abbott, 
1968: 92-93; Yonge & Thompson, 1976: 96, pi. 5, lower 
fig.; Lalli & Gilmer, 1982; Smith, 1998: 811-814; Light, 
2003). Jeffreys (1867: 175) and other early authors referred 
to still earlier descriptions and illustrations by authors as 
early as Colonna (1616). Dollfus & Dautzenberg (1932: pi. 
13, lower fig.) republished Colonna’s (1616) plate, showing 
a clear illustration of a living Janthina animal with inverted 
shell, float, strongly protruding head and snout with forked 
cephalic tentacles, and protruding, subdivided odontophore 
and radula. The species illustrated is Janthina globosa, to 
judge from the evenly subspherical shell and the angular, 
protruding anterior end of the columella. Morch (1860: 
261-262) listed all descriptions of float formation known 
to him, including a still earlier one by Colonna (1606) and 
further descriptions and illustrations by early authors. He 
also listed reprints or translations of the excellent description 
by Coates (1825) in “Zoological Journ., vol. 3, p. 264. - 
Thompson. Ann. Philos, new ser. Vol. 10, p. 385. - Proceed. 
Bost. Journ. 1. 184. - Feruss. Bull. - Johnston Conchyl., 
p. 131” (Morch, 1860: 262, footnote). The drawings by 
Fraenkel (1927: figs 3^1; Fig. 8) illustrate the formation and 
attachment of a bubble particularly clearly. 
Wilson & Wilson (1956: pi. 1, figs 2-3), Bayer (1963: 
fig. 4) and Light (2003: figs 4-10) also illustrated bubble 
formation with photographs, although this subtle process 
is difficult to illustrate by this means. Yonge & Thompson 
(1976: 96) described bubble formation particularly clearly: 
“These surface-dwelling oceanic animals have a large float 
consisting of mucus-coated bubbles of air formed by the 
propodium which is raised, spoon-shaped, above the water 
surface to entrap an air bubble which, enclosed in mucus, is 
added to the base of the float below. The process takes under 
a minute and is repeated some ten times before a rest is taken. 
The compacted float is described as ‘springy and dry’”. One 
of the most thorough descriptions of Janthina anatomy and 
biology is by Simroth (1895: 5-26, pis 1-2). He listed six 
species collected by the Plankton Expedition, suggested two 
of them might be synonyms, and described their radulae, 
mantle cavity organs, tentacles and epipodia, foot, float and 
float formation, ontogeny, larvae and protoconchs. The early 
description by Delle Chiaje (1841: 104-110, pis. 67-68) 
is also thorough. Fretter & Graham (1962: 115) described 
the pedal mucus gland modifications clearly: “Across the 
anterior edge of the foot... runs a cleft marking the position 
of the anterior pedal mucus gland. Along the centre of the 
anterior half of the mesopodium ... runs a groove into which 
the sole gland discharges mucus; this groove is called the 
funnel and posteriorly it ends in a transverse fold covered 
with smaller longitudinal grooves and rich in gland cells. It 
