100 



THE VOYAGE OF H.M.S. CHALLENGER. 



the insertion of the velum, by a ring-canal (cc). From their apical junction arises a 

 peduncular canal (cp) which runs through the pedicle of the gonophore (or the apical 

 horn) to its insertion intd the bracteal cavity and opens here into the phyllocyst. 



Gonads. — The gonad, or sexual gland of each gonophore, is represented by the 

 manubrium, which depends from the apex of the subumbrella into its cavity. In the 

 mature state it usually fills about the apical half of that cavity, but in many cases the 

 entire cavity, and sometimes by further growth it becomes much larger than the latter, 

 and is widely prominent through its distal opening (for example, in Lilyopsis, Des- 

 mophyes, Vogtia, PL XXX.). Each gonad is a simple, cylindrical, ovate, or spindle- 

 shaped sac, and contains a central cavity, which is closed at the distal end, whilst it 

 opens at the proximal end into the peduncular canal. The thick wall of the cavity 

 consists of three different layers, outside a covering exodermal epithelium, and inside 

 a vibratile entodermal epithelium, which includes the cavity (spadix) ; between these is a 

 layer of sexual cells, which are originally derived from the exoderm. They produce 

 a number of large ovules (usually between twenty and forty) in the female, and in- 

 numerable small zoosperms in the male gonophores. The ovaria or female gonads are 

 usually somewhat rounded, ovate or club-shaped, colourless (PI. XXVIII. fig. 4 ; 

 PI. XXXIV. figs. 13, 14, &c). The spermaria or male gonads are rather elongated, 

 cylindrical, or fusiform, often vividly coloured (yellow, orange, red) (PL XXVIII. fig. 6 ; 

 PL XXXIV. figs. 11, 1^, &c). 



Ontogeny. — The development of the Calyconectse from the fertilised egg has hitherto 

 been very little known. The first observations were made in the spring of 1853 by 

 Gegenbaur in Messina. 1 He observed the segmentation of the egg of Diphyes sieboldii, 

 and the development from it of a larva, which is a peculiarly modified medusome, 

 composed of a simple nectophore and a cylindrical sac-shaped larval body, which is 

 attached externally to the ventral side of the nectophore. In my opinion the 

 mouthless larval body is the original siphon, protruded through a ventral fissure of the 

 nectophore. From its base the primary tentacle arises afterwards. I call this larva 

 Calyconula. 



A similar Calyconula is developed from the egg of Galeolaria aurantiaca ( = Epibidia 

 aurantiaca), which Metschnikoff described in 1874. 2 The Calyconula of Hippopodius 

 gleba, described by the same author, 3 exhibits still more distinctly the dislocation of the 

 siphon, the axis of which is perpendicular to that of its nectophore, in the subumbrellar 

 cavity of which it was originally placed. The remnant of the ventral fissure of the 

 bilateral umbrella is yet partly visible. 



The Calyconula of a Monophyid (Muggi&a hockii), and its development from the egg 

 as well as its metamorphosis, were described in 1882 by Chun. 4 This larva developed 



1 7, p. 332, Taf. xvi. figs. 12-21. 

 3 Loc. cit., p. 46, Taf. xi. figs. 5-S. 



; 85, p. 39, Taf. vi., vii. 



1 86, p. 9, Taf. xvii. figs. 6, 7. 



