254 THE VOYAGE OF H.M.S. CHALLENGER. 



(fig. 9), covers the two poles of the sagittal axis (dorsal and ventral pole), and lies there- 

 fore immediately beyond the two lowermost nectophores. Between the former and the 

 latter (in two crossed diagonal axes) lie two pairs of opposite bracts of medium size (fig. 

 10). Each bract has a concave ventral or axial face, and a convex dorsal or abaxial face, 

 in the median line of which arises a prominent crest or keel (bd). A simple bracteal canal 

 (cb) runs near the ventral side, in the median line, and ends blindly near the distal apex. 

 The two lateral margins form a pair of thin lamellar wings, each with a prominent tooth 

 towards the distal end. The base of the bract (bb) bears a curved hook, for insertion 

 into the trunk ; and the opposite distal apex is provided with a bunch of cnidocysts. 

 These are wanting, however, in the two large lateral bracts, which appear straight in 

 profile (fig. 12), whilst the other six have a sigmoidal curve (fig. 10). The two large and 

 very vigorous lateral bracts may act in the rapidly swimming animal like the so-called 

 "swords" in a sailing boat. Nectalia loligo has a more rapid swimming motion than 

 any other known Physonect, and agrees in this with Diphyes, Sagitta, and Loligo. 



Patyons (q). — Immediately beyond the corona of bracts is placed a corona of palpons 

 or tasters, comparable to that of Physophora, but much less developed. The number of 

 palpons which are attached to the trunk close inside the base of the bracts seems to 

 correspond to that of the latter. Their body is a long and slender cylindrical tubule, 

 very mobile and flexible. The palpons may be perhaps better called cystons, since they 

 seem to possess a mouth-opening at the distal end (fig. 2, qo ?). I could, however, not 

 be absolutely certain on this point. 



Siphons (figs. 1, 2, s, 13). — The number of fully-developed siphons was in the single 

 specimen observed four, and they were attached to the base of the vesicular trunk of 

 the siphosome, inside the corona of palpons. When fully expanded and prominent 

 between the bracts (fig. l) the siphons were longer than the latter (up to 30 mm.). 

 The short pedicle of the siphon bears a pyriform basigaster (sb), and upon this an 

 ovate, very dilatable stomach (sm) ; its inside exhibits eight to twelve or sixteen longi- 

 tudinal rows of prominent, glandular, red-coloured villi (sv). The following proboscis 

 (sr) is a cylindrical, very mobile tube with a thick muscular wall; its entoderm is in some 

 siphons red. The mouth at its distal end is often dilated, and its opening, also reddish, 

 scpuare or provided with four short lobes (so). 



Tentacles (figs. 1, t, 2, 14). — Each siphon bears at its base a long tentacle, 

 beset with a series of numerous tentilla. The latter (fig. 14) have a long pedicle 

 (ts), a large cnidosac (tk), and a simple small terminal filament ((/*). The cnidosac 

 has a peculiar form, being composed of two large subspherical ampullae (one proximal, 

 tk u and one distal, tk ul ), and between both a cylindrical middle part (tk n ), which 

 contains a large cnidobattery (tk ly ). This latter is a long spiral riband of four to 

 five coils, composed of innumerable small paliform cnidocysts (fig. 15) and two lateral 

 rows of large ellipsoidal cnidocysts (fig. 16). 



