MKIirS.E OF THE WORLD. 



and least-developed tentacles. Thus tentacles (i) and (7), the oldest and youngest, are 

 situated at the ends of the two simple radial-canals, while tentacles (2, 2) and (3, 3), the 

 second and third in order of age, are found at the hases of the two forked canals. In addition 

 to these there are the interradial sets of tentacles (4, 4), (5, 5) and (6, 6) in order of age; 

 and thus the medusa has 12 tentacles, 6 radial and 6 interradial. 



It is remarkable that through a peculiar process of growth and budding each tentacle- 

 bulb is successively developed into a small medusa which resembles the adult and is set free 

 into the water. The oldest tentacle is the first to develop into a medusa and be set free, and 

 the others follow in the order of their age until all of the tentacles have been cast off. They 

 are immediately replaced, however, by new tentacles, but after every one of the original 12 

 tentacles has been developed into a new medusa, the process of forming medusae declines 

 and finally ceases, and then the parent medusa becomes sexually mature. 



The first stage in the transformation of a tentacle-bulb into a new medusa is the appear- 

 ance of a hernia-like outgrowth upon the floor of the subumbrella close to the tentacle-bulb. 

 This hernia-like pro|ection, which is composed of both ectoderm and entoderm and has 

 its cavity connected with a radial-canal or the circular vessel of the medusa, is destined 

 to form the manubrium of the new medusa. Soon after it begins to develop 2 pointed out- 

 growths appear on the sides of the ad|acent tentacle-bulb and these soon develop into new 

 tentacles. These outgrowing tentacles become larger and soon a still younger pair appear 

 farther out on the side of the original tentacle-bulb and these are soon followed by another 

 pair of tentacles, between the original pair of side branches and the margin of the medusa. 

 Before this has taken place, however, 4 short canals (the bifurcated radial-canals of the 

 future medusa) develop and the circular canal completes its circuit by coalescence. 



An opening then appears in the velum of the parent medusa immediately below the manu- 

 brium of the developing medusa and this constitutes the velar opening of the new animal. 

 The manubrium becomes cruciform in cross-section and finally the new medusa is con- 

 stricted off and is set free with 6 radial-canals, 5 well-developed and 6 small, immature ten- 

 tacles and a velum (plate 19, fig. i). Even before the young medusa is cast off a hernia-like 

 outgrowth has developed near the base of its oldest tentacle preparatory to a repetition of 

 the process of budding. In this remarkable process of budding we see that the simple radial- 

 canals, the nr.g-canal, the velum, and the oldest tentacle are stolen directly, so to speak, from 

 the parent medusa. The forked canals, manubrium, and younger tentacles are new growths, 

 and thus the bud is not compelled to develop all of its organs anew. The budded medusae are 

 very hardy when detached and swim actively about, and soon develop new medusae out 

 of their tentacle-bulbs. 



The manubrium of the mature medusa is about as long as the depth of the bell-cavity. 

 There is an enlargement near the middle of its length; the 4 simple lips are well developed 

 and cruciform. The gonads occupy 4 interradial situations in the upper part of the ecto- 

 dermal wall of the stomach. After the budding medusae have been set free the gonads become 

 mature and the ova are large and project from the interradial surfaces of the stomach. They 

 are finally dehisced into the water. The entoderm of the manubrium, tentacle-bulbs, and 

 circular canal is ocher-yellow, all other parts being transparent. 



This medusa was abundant at Tortugas, Florida, from May 21 to June 4, 1899; and a 

 few have been found early in June of every subsequent year. It is very active and thrives 

 well in confinement. 



Tribe WILLIADI. 

 Genus PROBOSCIDACTYLA Brandt, 1838. 



Proboscidactyla, BRANDT, 1838, Mem. Acad. Imp. St. Petersbourg, Sci. Nat., ser. 6, tome 4, p. 390. BROWNE, 1904, Hydro- 

 medusz Maldive Islands, p. 725; 1901;, Cevlon Pearl Oyster Report No. 27, Medusa?, p. 135. MAAS, 1904, Sitzungsbrr, 

 math.-phys. Klasse kg!. Bavrr. Akad. \\~issenschaften, Bd. 34, p. 438; 1905, Hydromedusen der Siboga Expedition, 

 p. 20 BIGELOW, H. B., 1909, Mem. Museum Comp. Zool. at Harvard College, vol. 37, p. 218. 



It'ilhta, McCRADV, 1857, Gymn. Charleston Harbor, p. 47. 



It'illia, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 346. AGASSIZ, A., 1865, North Amcr. Acal., p. 171 . VERRILL, 1873, 

 Report Commiss. Fish and Fisheries for 1871-72, p. 735. 



n\<r,mnola+ Dicranocanna J rWilletta+ Proboicidaayln, HAECKEL, 1879, Syst. der Medusen, pp. 151, 156, 157, 159. 



It'illia, FEVVKES, 1882, Bull. Mus. Comp. Zool. at Harvard College, vol. 9, No. 8, p. 299; 1884, Mem. Mus. Comp. Zool. at 

 Harvard College, vol. 9, No. 3. plate <;, fig. 19. 



ll'ilhiii, HUXLEY, 1891, Anatomy of Invcrtcbrated Animals, p. 120. 





