REPORT ON THE SIPHONOPHORiE. 201 



end of the bracts, similar to that which is found in some Athorula larvae of Agalmidee 

 (PI. XXI. figs. 7, 10, 12). Another similar form, but with more numerous and slender 

 bracts, was found in a preparation in the Challenger collection (Athoria bractealis). 

 It was insufficiently preserved. Possibly these small and delicate Physonects have already 

 been seen by former observers, but regarded as mere larva?. 



The entire corm of these monogastric Athoridse represents a single cormidium, and 

 may be regarded as a medusome, the umbrella of which is the pneumatophore, and the 

 manubrium the central siphon. From the proximal base of the latter is produced by 

 budding a corona of secondary medusomes ; each of these is again composed of a 

 modified umbrella (the bract) and a manubrium (the palpon) ; the palpacle, which is 

 attached to the base of each palpon, is the persistent tentacle. The gonophores, which 

 are developed beyond the palpons, represent a second corona of medusomes, which 

 become sexually mature. The small nectosac which occupies the distal end of the bracts 

 in Athoria is of special interest, since it demonstrates that the bracts are modified 

 urnbrellse. 



Syncypsis of the Genera of Athoridse. 



Bracts with a rudimentary nectosac on the distal end. Corms monoecious. Tentilla without 



involucrum, . . . . . . . . . .37. Athoria. 



Bracts without rudimentary nectosac. Corms dioecious. Tentilla with an involucrate 



cnidoband, .......... 38. Athoralia. 



Genus 37. Athoria, 1 Haeckel, 1888. 



Athoria, Hkl., System der Siphonophoren, p. 39. 



Definition. — Athoridse with a rudimentary nectosac at the distal end of the bracts. 

 Tentilla with a naked spiral cnidoband, without involucrum. Corms monoecious. 



The genus Athona is remarkable for the possession of a rudimentary subumbrella, a 

 small campanulate nectosac at the distal end of the bracts ; its mouth is armed with four 

 groups of cnidocysts which may be regarded as small rudiments of tentacles. They 

 agree in this character with the genus Rhodophysa among the Anthophysidse (Genus 58) 

 and with the Athorula larvae mentioned above (p. 200). The tentilla are similar to those 

 of Halistemma and Forskalia, with a naked spiral cnidoband. Athoria larvahs 

 (PI. XXI. figs. 5-8) was observed living by me in Ceylon. A similar species, but 

 larger, with more numerous and slender bracts, was found in a mounting of the Challenger 

 collection (from Station 288, South Pacific). It was not well enough preserved to be 

 described and figured. 



1 Athoria, name of an Oceanid, 'ASu^ia. 

 (ZOOL. CHALL. EXP. — PART LXXVII. — 1888.) Hhhh 26 



