534 MEDUSiE OF THE WORLD. 



This species is found in Massachusetts Bay and off the northern coasts of Europe from 

 England to Norway. Clark reports it from Norton Sound, Alaska, and Bigelow from Labra- 

 dor and Newfoundland. It is only locally common on the New Enijland coast. 



It ma\' be distinguished from //. octonullatiis hv its more slender hell and stalk, its large 

 mart'inal anchors, and the greater number and smaller size of the genital sacs upon the gonads. 

 Kishinouye, 1910, records a form from Japan which resembles H. auricula excepting that 

 each gonad consists of onh' two rows of saccules. He calls this medusa H. tmuis. 



Haliclystus octoradiatus Clark. 



Lur^rnaria auriVu/a, Montagu, 1808, Trans. I.inn. Soc. London, vol. 9, p. 113, plate 7, fig. 5. — Sars, M., 1829, Biilragtil 

 Siidyr. Nalurhist., p. 34, taf. 4, fign. 1 to 13. — Johnston, 1838, Hist. British Zoophytes, p. 229, fig. 35. — AcASsiz, 1861, 

 Cent. Nat. Hist. V. S., vol. 4, p. 176. 



Lucfrnaria octoraJiaiaf Lamarci:, 1816, Hist. anim. sans vert., torn. 2, p. 474. — Stkf.nstri'P, 1859, Vidensk. MedJel. Nat. Keren. 

 Kjobenliavn, p. 108. — Sars, M., i860, Forhandl. Vid. Selsk. Christiania, p. 145. — Kkfkrstf.in, 1863, Zcit, wissen. Zool., 

 Bd. 12, p. 22, taf. I, fign. 1-3. — Taschenberg, 1877, Zcit. Gi-s. Naturw., Halle, p. 91, taf. 2, fig. 4. — Bergh, 1888, 

 Vidensk. Meddcl. Nat. For. Kjobenhavn, p. 214, fign. 1-3. 



Haliclysius ocioraJiaius, Clark, H. J., 1863, Jour. Boston Soc. Nat. Hist., vol. 7, p. 565. — Haeckel, 1S80, Syst. drr Medusen, 

 p. 388. — Levinsen, 1893, Vid. Meddel. Nat. Forcn. Kjobenhavn, (5), Bd. 4, p. 146. — Browne, 1896, Quart. Journ. Mic. 

 Sci., vol. 38, part, i, pp. 1-8, plate 1, 22 figs. — Hornell, 1893, Natural Science, London, vol. 3, p. 33 (abnormalities). — 

 Browne, 1895, Quart. Journ. Micros. Sci., ser. 2, vol. 38, p. i, plate i (variations). — Gross, 19<x3, Jena. Zeit. Naturw., 

 Bd. 33, p. 611, taf. 23, 24 (anatomical). — Beaumont, 1900, Proc. Roy. Irish Acad., Dublin, ser. 3, vol. 5, p. 808. — Maas, 

 1904, Result. Camp. Sci. Prince de Monaco, fasc. 28, p. 44. — Wietrzvkowski, 1909, Comptes Rcndus, Paris, tome 149, 

 p. 746. 



Disk 20 to 30 mm. wide and, with the stalk, 20 to 30 mm. high. Disk flat and about 

 2 to 3 times as broad as high. The 8 adradial arms are 45° apart, not grouped in 4 more 

 or less approximated pairs, as in H. aiiruuhi. .Arms very wide, concavities of bell-margin 

 shallow. Each arm bears a terminal cluster of 30 to 60 tentacles, instead of 100 or more, 

 as in H. auricula. The 8 perradial and interradial marginal anchors (coUetocvstophores) are 

 egg-shaped, and about one-fourth as long as diameter of stalk. Stalk cylindrical, without 

 longitudinal furrows, 4-chambered. and with 4 interradial, longitudinal strands of muscle- 

 fibers. There are 8 separate gonads which do not extend cjuite to the end ot the arms or to the 

 aboral septa. Each gonad contains only 2 rows of alternately arranged, large, genital sacs. 



Color quite variable, being either gravish-yellow, brownish-yellow, or gravish-hrown. 



Found on the North .Atlantic coasts of Europe, on the Greenland coast, and at Spitzbergen. 



The most complete descriptions of this species are given h\ Sars, 1829; Keferstein, 1863; 

 Browne, 1895; and Gross, 1900. Its variations have been studied by Hornell, 1893, and 

 by Browne, 1896. The abnormal forms are very irregular, symmetrical variations rarely 

 appearing. The medusa is one of the most variable known. \t Jersev, England, according 

 to Hornell, 66 per cent of the specimens were abnormal in some respect; but at Phniouth, 

 according to Browne, only 34 per cent were abnormal and the aberrations were quite different 

 from those found at Jersey. We are unable to determine whether this difference is fostered by 

 isolation or is due to the effect of local influences in the environments of Plymouth and Jersey. 

 It may also be due to a difference in variative tendency in the medusae of the two places. 

 The development of//, octoradiatus has been studied by Bergh, 1888. The egg is fertilized 

 after being discharged into the water and then it retracts somewhat from the vitelline mem- 

 brane. 2 polar bodies are found; the segmentation is total and equal, and there is no cleavage 

 cavity. The entoderm appears to be formed by polar ingression of cells into the center of the 

 solid morula which is at first spherical but attei-wards it elongates into a rod-like form, which 

 becomes so long and narrow that the entodermal cells come to be arranged one after another 

 in a single row as in the planula oi Solmundella. The planula of//, octoradiata is not ciliated, 

 however, but creeps about by means of worm-like movements. It then attaches itself by the 

 anterior end as do other planuise of Scxphomcdusrc. At first the tentacles are not united into 

 definite clusters but are distributed around the bell-margin, but 8 tentacles are more or less 

 isolated and lie in the perradial and interradial radii. These form the marginal anchors. 



The best description of the development of the planula is given by Wietrzykowski, igog 

 (see Appendix to this Volume). 



Bergh, 1888, describes an abnormal specimen of //. octoradiatus with a small bud 

 arising from the side of its bell. 



