MEDUSAE OF WOODS HOLE REGION. 



61 



SPHffiRONECTES Huxley (1859). 



Sphaeronectes gracilis (Clans). Text cut. 



Mtmophyes gracilis Claus, Schriften Zoologischer Institut Wien, isti, p. 29. 



tKptophy&a inermis Fewkes, Bulletin Museum Comparative Zoology, Vol. VI, 1881, p. 143. 



The figure given herewith will afford a generally sufficient means of identification. Fewkes repi >rts 

 the species from New 7 port, R. I. Other than this I am not aware 

 that it has been found within this region. 



Cystonect^e. 



With large vesicular pneumatophore only, no nectophores or 

 bracts. 



PHYSALIA Lamarck (1S01). 



Physalia pelagica Bosc. 



Physalia pelagica Bosc, Histoire Naturelle dcs Vers, Tome II, p, 168, 1802. 



Physalia arethusa Tilesius, in Krusenterns Reise, 1812, p. 91. 



Physalia earavella Eschscholtz, System der Acalephen, 1829, p. 160. 



Physalia pelagica Lamarck, Animaux sans Vertebres, 2d edition, 1840, p. 92. 

 Huxley, Oceanic Hydrozoa, 1859, p. 100. 



Physalia arethusa L. Agassiz, Contributions to Natural History of the United 

 States, 1862, p. 335. Chun, Die Siphonophoren der Plankton-Expedi- 

 tion, 1897, p. 89. 



This is, for several reasons, the best known of siphonophores. 

 Its large size and conspicuous float, ami long and numerous ten- 

 tacles with their powerful batteries of nematocysts, have combined 

 to render the species noteworthy. These alone are generally 



sufficient for its easy identification. The large and beautifully colored pneumatophore, capable of nice 

 adjustments to wind and wave, the graceful and pendulus tentacles, the languid, passively floating 

 habit of the creature, and last, if not least, its venomous repute, render its presence a center of eager 

 interest to observers. It is a fairly familiar object in Vineyard Sound and adjacent water.-, at times 

 as many as fifty specimens being taken during a single cruise within a few miles of Woods Hole. 



Spll&roncc/cs yrarilis. After Mayer. 



THE SCYPHOMEDUSiE. 



In general form, structure, habits, and distribution the Seyphomedusa^ have 

 much in common with the Hydromedusa> and probably sustain a much closer 

 relation to them than to any other of the ctelenterate classes. As a rule they are of 

 larger size, somewhat sluggish in habits, the margin of the umbrella is more or less 

 evidently lobed, and there is usually a large manubrium which is provided with large 

 oral lobes, often complexly fimbriated or plaited. The body is also usually much 

 thicker and more rigid than in the Hydromeduspe, and in some of the orders it is 

 provided with a well-organized muscular system. 



As in the Hydromedusa? there is usually a well-detined alternation of genera- 

 tions, though with notable exceptions in some of the orders, and in all there seems 

 to be a' tendency toward the suppression of the nonsexual stage, which is frequently 

 quite inconspicuous and more or less temporary. In contrast with this phase in the 

 Hydromedusffi, the metamorphism is usually more extended and arises differently. — 

 namely, by a process of transverse fission, known as strobilization, the entire body of 

 the polyp constricting into a series of segments which eventually become free larval 



