ANTHOMKDUS.E PENNARIA. I'.") 



This hydroid is one of the earliest forms known, yet reliable information from the system- 

 atic standpoint is still incomplete. One of the best modern descriptions is that <>t Allman, 

 1872. I believe the American " Penmn-in tinn-lln" to be closely related to P. Jiiliilm. 

 The only difference appears to be that the terminal ramuli in P. disticha are ringed through- 

 out, whereas in P. tiarella they are usually ringed only at base and summit, although I have 

 seen an occasional one ringed throughout in the American hydroid. (See VV. S. Wallace, 

 1908, Year Book of the Carnegie Institution.) 



In the European hydroid, P. Jisticha, the stems become about 150 to 175 mm. high. The 

 main stem is slightly zigzag and with a uniform growth-curve from base to summit. There are 

 about forty side branches, regularly alternate. Perisarc annulated at the origins of the branches 

 and on the ultimate hydranth-bearing ramuli. Hydranths flask-shaped, with a single verticil 

 of about 10 to 13 basal filiform tentacles each about I to 2 times as long as the body of the 

 hydranth, and each ending in a blunt, slightly swollen tip. About 20 short, stiff, knobbed 

 tentacles, irregularly arranged in 3 verticils, arise from the sides of the hydranth above the 

 basal verticil of tentacles. The medusa-buds are similar to those of Pennaria tiarella and 

 are without ectodermal ocelli upon their tentacle-bulbs. The medusa? usually wither upon 

 the hydroid without being set free, but this often occurs also in P. tiarella, especially in the 

 warm water of Florida. 



Weismann, 1883, found that the germ-cells originate in the ectoderm of the inner layer 

 of the bell-nucleus and do not wander from their place of origin, becoming mature in the 

 free medusa, or when the medusa-bud is ripe. 



Very elaborate studies upon regeneration, regulation, and restitution in injured colonies 

 were carried out by Cast and Godewski, 1903. 



This hydroid is found in the Mediterranean. Pictet, 1893, found it at Amboina, Malay 

 Archipelago. It occurs at Naples, Italy, from May to November. 



Pennaria tiarella McCrady (American). 



Plate I, figs. 2-5. 

 REFERENCES TO THE AMERICAN HYDROID. 



G/obiceps tiarella, AOASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 344. AVER, 1852, Proc. Boston Soc. Nat. Hist., vol. 4, 

 p. 193. HAECKEL, 1879, Syst. der Mejusen, p. 39. 



Pennarin tiarella, AGASSIZ, A., 1865, North. Amer. Acal.,p. 187, figs. 311-315. NUTTING, 1901, Bull. U. S. Fish Commission 

 for 1899, vol. 19, pp. 337, 374, figs. 14, 83. HARGITT, 1900, Amer. Naturalist, vol. 34, p. 387, plates 1-4, 36 figs.; 

 Bull, of the Bureau of Fisheries U. S., for 1904, vol. 24, p. 32, plate 3; 1904, Archiv. fur entwickrlungs-mech. organ- 

 ism, Bd. 18, p. 453, taf. 24-28; 1902, Amer. Naturalist, vol. 35, p. 31 1, figs. 8, 9; p. 597, fig. 36; 1899, Biol. Bulletin 

 Woods Hole, vol. i, p. 35-40, 6 figs, (grafting eiperiments); 1900, Science, New series, vol. 12, p. 340; and 1901, 

 Biol. Bulletin Woods Hole, vol. 2, p. 223 (variations of hydroids and medus.T.) MCCRADY, 1857, Gymn. Charleston 

 Harbor, p. 51. SMALLWOOD, 1899, American Naturalist, vol. 33, p. 861, 7 figs, (histology). HARTLACB, 1907, Nor- 

 disches Plankton, Nr. 12, p. 72, figs. 68-70. GOLDFARB, 1906, Journ. Experimental Zool., vol. 3, p. 148 (regeneration). 



Pennaria liarclla=(P. svmmetrica, CLARKE), CONGDON, 1907, Proc. American Acad. Arts and Sci., vol. 42, p. 464. 



Pennaria, j/>., THACHER, 1903. Biol. Bulletin, vol. 4, p. 96. 



I'tnritiria gibbosa, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 278, 344; vol. 3, plate 15, figs. I, 2. 



Halcord\Ie tiarella, ALLMAN, i87i,Monog. Tubul. Hydroiils, p. 369. 



Kuforyne elegant, LEIDV, 1855, Marine Invert. N. J. and R. I., p. 4, plate 10, figs. 1-5. 



THE AMERICAN PENNARIA. 



Medusa. The bell is about 2 mm. in height, and is ellipsoidal, being higher than it is 

 broad. Bell-walls very thin, flexible, and much distorted by the remarkably large ova, which 

 are situated within the ectoderm of the manubrium and often fill the entire cavity of the bell. 

 There are 4 small, rudimentary tentacle-bulbs, without ocelli, I at the base of each radial- 

 canal. Radial-canals straight and quite broad. Velum wide and powerful. Manubrium 

 of male more slender than that of female, the latter being usually greatly distended with 4 or 

 5 large ova. Several ova are often set free into the water before the medusa is liberated from 

 the hydroid stock. The medusa is commonly mature at the time of its liberation, and it is 

 probable that it does not usually survive for more than a few hours, though Dr. A. Agassiz 

 has maintained them alive for several weeks. The entoderm of the manubrium is rose-pink, 

 and there are a number of deep-pink blotches in the entoderm of each radial-canal. The 

 entoderm of the tentacle-bulbs is pearly-white, as are also the eggs within the manubrium. 

 These colors vary considerably in hue and may be almost white. 



