AXTHflMKDrS.F. PODOrORYXE. 130 



for observing their growth and development while studying at Dr. Alexander Agassiz's labor- 

 atory at Newport, in 1892-96. 



In 188 1-82 de \ arenne concluded that both eggs and sperm-cells originate in the entoderm 

 of the crenosarc of the hydroid and afterwards migrate into the medusa-bud. The more 

 careful researches ot Weismann, 1883, however, refuted this view, showing that the male 

 germ-cells originate in the ectoderm of the budding medusa, but do not wander from their 

 place of origin. On the other hand, the female germ-cells may possibly originate in the ecto- 

 derm; if so they soon wander into the entoderm of the budding gonophore, then into the spadix 

 of the medusa-bud and finally into the ectoderm of the manubrium of the medusa. According 

 tii rlie later studies of Ishikawa and of Bunting, however, the egg-cells t,ri^inntf in the min- 

 der m dl the medusa-bud and afterwards migrate into the ectoderm. 



Plate 12, figs. 5 to 9; plate 11, figs, i to 5. 



Adult medusa. Bell usually somewhat pynform in shape and about I mm. in height. 

 Gelatinous substance very soft and flexible, so much so, indeed, that the medusa is often found 

 to be much distorted and shriveled by the powerful contractions of the circular muscles. Very 

 frequently this contraction causes deep interradial furrows to appear upon the surface of the 

 bell, in the meridian of the radiating muscles of the subumbrella, and I believe that this 

 appearance led Fewkes, 1881, to describe one ot these contracted medusae as a new genus: 

 "Mabella gracilis." There are usually 8, but sometimes 16 (plate 13, fig. 5), long, marginal 

 tentacles with well-developed basal bulbs. These tentacles are quite stift and are carried 

 curled upward. The tentacle-bulbs are large and are filled with entodermal pigment. The 

 velum is wide. There are 4 straight, slender, radial tubes. The manubrium is furnished 

 with a well-developed peduncle (plate 12, figs. 6 to 9), which is quadratic in cross-section. 

 The peduncle has the shape of a frustum of a pyramid, and it extends about one-third the 

 distance from the inner apex of the bell-cavity toward the velar opening. The 4 radial tubes 

 extend down the 4 angles of the pyramid into the gastric part of the manubrium. The gastric- 

 portion of the manuhrium is short and the mouth-opening is situated at the lower extremity of 

 a short tubular neck. There are no prominent lips. 4 radially situated, oral tentacles arise 

 from the sides of the neck. These oral tentacles are quite flexible. They taper gradually and 

 end each in a single, knob-shaped cluster of nematocyst-cells. Medusa-buds are produced 

 upon the sides ot the stomach. These buds arise in the interradn (plate 12, tig. 7), and one 

 usually sees 4 or 5 of them in various stages of development. The place and time of appear- 

 ance of these medusa-buds appear to follow the law demonstrated by Chun, 1895, in Rnthkta 

 ni tripnin'tata. When set free the young medusa has 8 marginal tentacles. It is interesting to 

 observe that while the medusae are still attached to the manubrium of the mother they 

 themselves begin to develop medusa-buds upon the sides of their manubria (plate 12, tig. 7). 

 The entoderm of the tentacle-bulbs is of a delicate salmon-red. The manubrium is some- 

 times colorless and sometimes salmon-red. 



This medusa is very abundant at Newport, Rhode Island, late in the summer, when it 

 occurs in vast swarms which cause the water, when disturbed at night, to glow with ;i bluish 

 phosphorescence. A large swarm was found in the St. Mary's River, Maryland, near the 

 mouth of the Potomac, in November, 1905; and I have also taken it at Beaufort, North Caro- 

 lina, late in November. It has not been seen at Tortugas, Florida, 



This species is readily distinguished from Podocoryne rarnea by its much smaller size. 

 Also the manubrium is provided with a well-developed peduncle, while in I 1 , ctirnnt there is no 

 peduncle. P. fiilgnrntis is very delicate and flexible, while P. faniea is tough and relatively 

 inflexible, 



A PoJdiat \iii- found at Beaufort, North Carolina, by Professor Brooks, is probably the 

 hydroid of this medusa. The tentacles are usually in whorls of 5. 



