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



phorse, we find resemblances to different families. The pneumatophore resembles by its 

 simple structure that of the Athoridae and Apolemidse, and that of the young Physalidae 

 (Alophota, PI. XXVI. figs. 1, 2); the pericystic cavity is simple and has not the radial 

 pouches of most Physonects, nor the hypocystic villi of the Rhizophysidse and Epibulidae. 

 The corona of palpons between float and siphon is similar to that of Epibulia (PL XXII. 

 fig. 6), and also to that of the Discolabidse and Anthophysidae. The single tentacle, with its 

 series of simple filiform tentilla, resembles that of Epibulia and Nectophysa (PL XXII. 

 figs. 5, 6). The structure of the single siphon, with its hepatic villi, and of the monoclinic 

 gonodendron, is the same as in the PJiizophysidaB and Physalidae. 



Genus 65. Cystalia, 1 Haeckel, 1888. 

 Cystalia, Hkl., System der Siphonophoren, p. 44. 



Definition. — Cystalidze with a tentacle, which bears a series of simple filiform tentilla. 

 A single large monostylic gonodendron is attached to the base of the single siphon. 



The genus Cystalia, as the only known form of monogastric Cystalidse, exhibits 

 the peculiar structure described above of this family. Supposing that other genera, 

 belonging to it, may sometimes be observed, we assume as a generic character of Cystalia 

 the structure of the single tentacle, which is similar to that of Aurophysa, Nectophysa, 

 and Epibulia. It bears a series of simple lateral branches, which remain cylindrical 

 filaments, without terminal appendages. On the medusiform larvae (Cystonula, PL 

 XXII. figs. 1-4), which may perhaps belong to this genus, compare p. 315. 



Cystalia monogastrica, n. sp. (PL XXII. figs. 1-5). 



Cystalia larvatis et Cystalia challenger i, Hkl., 95, p. 44. 



Habitat— South Pacific; Station 288, October 21, 1875; lat. 40° 3' S., long. 

 132° 58' W.; surface. 



Indian Ocean, Ceylon, Belligemma, December 1881 (Haeckel). 



Corm (fig. 5). — The monogastric corm, represented in fig. 5 in the expanded state, 

 has a length of 10 to 12 mm. It is to be regarded as a single cormidium, composed of 

 a sterile axial medusome and two groups of peripheral medusomes, sterile palpons and 

 fertile gonophores. The large axial medusome consists of a pyriform pneumatophore 

 and a large spindle-shaped siphon, with a single tentacle ; the siphon corresponds to the 

 manubrium, and the float to the modified umbrella of the original Medusa. The short 

 pedicle of the siphon, which connects it with the base of the float, may be regarded as 

 the axial trunk of the corm, from which the corona of palpons as well as the large ventral 



1 Ctjstalia = Sea-bladder, xt/aru, chta,. 



