84 
THE YOYAGE OE H.M.S. CHALLENGER. 
of the latter is situated the sessile spermatocyst ; this organ is yellow in colour and 
sausage-shaped, bent in the middle ; when extended it measured 7 mm. long ; it was 
full of semen. The vaginal duct is short, about one-third of the length of the sperma- 
theca, widening below to form the vagina (fig. 17, c) ; both portions are lined with a strong 
cuticle. The mucous gland is whitish ; the more yellowish albuminiparous gland is 
situated on its anterior and inner side. The whitish tongue-shaped vestibulo-vaginal 
gland measures 1’5 mm. long, and is sessile. 
Whether the form investigated here is merely a varietyof Ceratosoma cornigerum, or 
is a distinct species, must be left for the present undecided. The armature of the tongue, 
and perhaps the structure of the genital apparatus, might support the latter view. 
Archidoris, Bergh. 
Archidoris, Bergh, Malacolog. IJntersuch. (in Semper, Reisen im Archip. d. Philipp., Th. II. 
Bd. ii.). Heft xiv., 1878, p. 616; Supplementheft i., 1880, pp. 33-35. 
„ Bergh, On the Nudibr. Gastr. Moll, of the North Pacific Ocean (in Dali, Scientific 
Results of the Exploration of Alaska, vol. i., art v.), part 1, 1879, pp. 106-108 
(162-164). 
Corpus non durum, subdepressum ; dorso granuloso vel tuberculoso. Tentacula 
brevia, crassa, sulco marginali externo. Branchia (retractilis) e foliistri- vel quadripinnatis 
sat paucis formata. Podarium sat latum, margine anteriore superficialiter sulcatum. 
Armatura labialis nulla. Radula rhachide nuda, pleuris multidentatis ; dentes 
hamati. — Penis inermis ; vagina inermis. 
When Linnaeus founded the genus Doris , in the tenth edition of his Systema Naturae 
(1758), he only referred a single species to it, — his Doris verrucosa. 1 This species, 
founded solely on the figures of Seba and Rumphius, is probably indeterminable, and the 
Doris of the tenth edition of the Systema Naturae should, therefore, not have been 
retained in subsequent editions. In the twelfth edition (1767) the genus includes three 
other forms, — Doris bilamellata, Doris Icevis, and Doris argo. besides Doris verrucosa, 
which still figures as the first species. One of these three should become the type of the 
restricted genus, but which ? It is much better to do away altogether with the name 
Doris as a generic designation (especially as Linnaeus also used it in another sense for the 
animal of various shell-bearing molluscs), and with this view I have formed the genus 
Archidoris. 
This generic group, which is congeneric with the first of the sections established by 
Alder and Hancock in their systematic prospectus, 2 is rather distinctly marked. The 
1 Bergh, Malacolog. Untersuch., loc. cit., Heftx., 1876, p. 388. 
2 Monogr. of Brit. Nudibr. Moll., part vii., p. xvi., 1855. 
