. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 104 ACTINIARIA The mesenterial filaments are only present on the mesenteries of the first order. The ventral direc- tive pairs are, however, devoid of ciUated streaks. Below the aboral prolongation of the siphonoglyphe the filament namely begins as a weakly developed, single cnido-glandular streak of inconsiderable dimension, gradually growing thicker and attaining its largest dimensions in the reproductive region. As in certain Zoantharia (for instance Isozoanthus gigantcus) and in the Ceriantharia the ciliated streaks have
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. 104 ACTINIARIA The mesenterial filaments are only present on the mesenteries of the first order. The ventral direc- tive pairs are, however, devoid of ciUated streaks. Below the aboral prolongation of the siphonoglyphe the filament namely begins as a weakly developed, single cnido-glandular streak of inconsiderable dimension, gradually growing thicker and attaining its largest dimensions in the reproductive region. As in certain Zoantharia (for instance Isozoanthus gigantcus) and in the Ceriantharia the ciliated streaks have probably here fused with the aboral prolongation of the siphonoglyphe and the actinopharynx, though the different parts of the filaments of the prolongation cannot be distinctly traced. Possibly the continuation of the sipho- noglyphe and the recurvated part correspond to the ciliated streaks, the folded parts to the cnido-glandular streak. The imperfect mesenteries are devoid of filaments. The ciliated streaks are of typical appearance. Only the mesenteries of the first cycle are fertile. The spe- cies is dioecious. The ovae are provided with a covering, decked by spines. L,arvae. (Synonymy and literature, compare Carl- gren 1906, p. 81). The larvae of tliis species, living on several hydroid- medusae, have been anatomically described before by my- self and by several other authors, wherefore I do not give any details of its anatomy here. The younger stadia with only 3 couples of mesenteries are disc-like (Carlgren 1906 fig. 6 a). Somewhat older stadia are a little more rounded, still older ones are more elongated and acuminated in the aboral end, only in the adult animal the body is cylindrical. The ex- terior aspect of the larvae in different stadia I have shown 1906 (textfig. 6). On the plate i, figs. 21—29 I have completed the series (all larvae sketched on the samef scale). The arrangement of the tentacles I have described before (1904). The first eight visible tentacl
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