MEDUSA OF WOODS HnLK REGION. 



33 



PERIGONIMUS Sars (1840). 



Perigonimus jonesii Osborn A: Hargitt. Text cut. 



Perigonimus jonesii Osborn & Hargitt, American Naturalist, Vol. XVIII, is94, p. 27. Hargitt, Mittheilungen Zoologischeu 

 Station, Neapel, Bd. 11, 1895. 



Bell hemispherical, with slight apical projection, about as high as broad, 2 mm. or slightly inure 

 Marginal tentacles 2, located on opposite sides, and with 2 additional tentacular bulbs at the inter- 

 mediate points; tentacles highly retractile ami often carried coiled within the bell cavity, especially 

 when the medusa is disturbed. Velum well developed; manubrium short, subquadratic, and with 

 simple, 4-Iobed mouth. Gonads undeveloped in specimens taken, and showing no evidences of 

 growth within a period of more than two weeks, during which they were 

 kepi in apparent health in the aquaria. 



Habitat. — Found only on the legs and abdominal appendages of the 

 common spider crab, Libinia, and taken from this source during several 

 seasons. 



DtiAribviion. — Long Island Sound, originally taken at Cold Spring 

 Harbor. 



EUPHYSA Forbes ( 1848). 



Euphysa virgulata A. Agassiz. 



Euphysa virffiUata A. Agassiz, North American Acalephse, 1865, p. 189. Haeckel, System 

 der Medusen, 1879, p. 33. 



Bell somewhat elongate oval or subrectangular in profile; tentacles 4, 

 but unequally developed, one being much longer and heavier than the 

 others; basal bulbs pinkish and extending upward along the radial canals 

 for a short distance; manubrium short and thick, cylindrical, and with an 

 accumulation of fat-like globules about its base; mouth simple; gonads 

 borne upon the manubrium. In size the medusa is from 8 to 10 mm. in 

 long diameter, slightly less in breadth. 



Coh rs. — Bases of tentacles with bright pigment, extending up the radial canal.-; manubrium 

 lowish; bell transparent. 



Distribution. — Nahant, Massachusetts Bay, W Is Hole. 



ni-nnniit- fOIH ■'■ 



vel- 



HYB0C0D0N L. Agassiz ( 1862). 

 Hybocodon prolifer L. Agassiz. PI. II, fig. 2. 



Hybocodon prolifer I.. Agassiz, Contributions i<» the Natural History of the United States, istvj. Vol. IV, p, 243. A. Agassiz. 

 North American Acalephse, 1865, p. 193. Allman, Monograph ofthe Gymnoblastic Hydroids, 1871, p. 122, Haeckel, 

 >\ stem 'lor Medusen, 1S79, p. 33. 



Bell stil (hemispherical, unsymmetrical, being humped upon one side adjacent to the single large 

 tentacle, the latter having a heavy, thick base and affording support for the proliferous secondary 

 medusa' which bud asexually therefrom. The tentacle is very long, the terminal two-thirds being 

 abundantly supplied with rings of nematocysts. Manubrium rather short, cylindrical, and with simple 



i ith. Gonads on walls of manubrium, where the ova develop directly into aetinul.c, several of 



which may be found in various stages of development at the same time. 



Developing actinulse and budding medusa^ are found at the same time, usually during the early 

 spring — March to May — though proliferous medusse seem to arise almost constantly, being present on 

 specimens taken in August. An examination of the histology of the gonads shows aspects of oogenesis 

 and development almost exactly similar t" those exhibited in Pennaria, < brymorpha, Tubularia crocea, 

 and others. Egg cleavage is so similar to that found in the last-named species as to lie almost 

 indistinguishable during corresponding phases. Ova which become active and begin development 

 show the same phenomena of absorption of their fellows as Doflein has pointed out in Tubularia 

 mesembryanthemum and Allen in ']'. crocea. It is not clear how fertilization occurs, since the early 



B. B. F. 1904—8 



