REPORT ON THE SLPHONOPHOR^E. 207 



uppermost turning often arises a series of short diverticula or villiform lateral branches 

 (compare 4, p. 18, Taf. vi. figs. 6-9, and 8, p. 315, Taf. xii. fig. 7). 



Siphosome. — The tubular trunk beyond the nectosome in all Apolemidaa is very 

 long, and attains in the extended state a length of two or three feet or more. It bears 

 a great number of ordinate cormidia, separated by long internodes of equal length. 

 These are naked in Dicymba and Apolemia (similar to those in the polygastric Caly- 

 conectse), whilst they are densely covered with innumerable bracts in Apolemopsis 

 (as in Agalmopsis). The trunk is much shortened in the highly contracted state ; 

 the internodes then nearly disappear and the entire corm is covered by a carapace of 

 scales, the densely crowded bracts. 



Cormidia. — The two subfamilies of Apoleruidse are similar in the general conforma- 

 tion of the cormidia, and the structure of their single parts ; they exhibit, however, 

 an important difference in their composition. Each cormidium of the Dicymbidaa has 

 only a single siphon and a single cyston, surrounded by numerous bracts and palpons ; 

 whereas in the Apolemopsidse each cormidium possesses several (two to four or more) 

 siphons, and the same number of cystons. The Dicyinbidse, therefore, have monogastric 

 cormidia (like the Rhizophysidse, Pis. XXIII., XXIV.), whilst the Apolemopsidse 

 possess polygastric cormidia (like the Salacidse, PI. XXV.). The number of bracts 

 (usually twenty to forty in each cormidium) seems to be in all Apolemidse about the 

 same as the number of palpons and palpacles, so that perhaps each bract, together with 

 an appertaining palpon and a single palpacle, represents originally a medusome, the 

 organs of which are modified and dislocated ; the bract corresponding to the umbrella, 

 the palpon to the manubrium, and the palpacle to the single tentacle. 



Bracts. — The hydrophyllia, as the metamorphosed umbrella? of the medusomes, 

 exhibit in all Apolemidse hitherto observed the same peculiar form. They are ovate, 

 club-shaped or pyriform, with rounded distal end and pointed proximal end ; the latter 

 is attached to the stem by a short pedicle, which is raised or lowered by a muscle. The 

 convex outside (exumbrella) is armed with numerous whitish patches composed of cnido- 

 cysts, whilst the concave inside (subumbrella) is smooth. Near the latter there runs in 

 the median line of the bract a simple bracteal canal, which arises from the axial canal 

 of the trunk and ends blindly towards the distal end ; sometimes it is provided, near 

 the latter, with a small cEecal diverticulum directed towards the lower face (compare 

 7, p. 320, Taf. xviii. figs. 1-3, and 8, p. 316, Taf. xii. fig. 8). 



Sipthons. — -The feeding polypites have in all Apolemidae the same structure ; the single 

 siphon in the monogastric cormidia of Dicymba (PI. XVIII. figs. 1, 2, s), however, is 

 relatively larger, whilst the several siphons (two to four or more) in the polygastric cormidia 

 of Apolemia are smaller, and are more like the palpons. The four segments of the 

 siphon (PI. XVIII. fig. 2, s) are usually distinct, and already very well represented in 

 the oldest figure, given by Lesueur. The short pedicle, to which is attached the single 



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