CARYBDEID^. 505 



Hydromedusae; for it constitutes the only important point of difference in the velar diaphragms 

 of the two^sorts of animals. The velarium is commonly bound to the wall of the subumbrella 

 by 4 solid, bracket-like supports, the frenulae, one of which is found in each perradius. There 

 is also a more or less complicated system of entodernial canals or pouches which extend into 

 the substance of the velarium from the gastrovascular space of the bell. 



There has been a tendency among modern authors to regard the velarium as being com- 

 posed of a series ot fused lappets, the pouches being remnants of lappet-pouches. We have 

 no proof, however, that this is the case, and the velarium in the youngest Charybdeidae yet 

 seen is as entire as in the adult. 



There are 4 groups of gastric cirri, or phacelli, in the interradial corners of the central 

 stomach, at the inner ends of the 4 interradial septa, and this feature alone would distinguish 

 these forms from the Hydromedusae in which no such structures have been observed. The 

 gonads, also, are entodermal instead of ectodermal when mature as in Hydromedusae. Both 

 the gonads and gastric cirri are structures of the subumbrella, as is also the entire muscular 

 system. 



There is a well-developed nerve-ring on the bell-cavity side of the subumbrella near the 

 margin. This ring forms 4 loops upward to the 4 perradial sense-organs (plate 57, fig. 2). 

 There are 8 ganglia upon the nerve-ring, 4 perradial and 4 interradial. Each of the perradial 

 ganglia sends off 2 nerve-roots, which pass through the gelatinous substance of the subumbrella 

 and fuse as they extend down the inner (centripetal) side of the stalk of the sensory-club. 

 The 4 interradial ganglia are situated at the bases of the tentacles into which they probably 

 send nerve-fibers. 



The Carybdeidag are inhabitants of the warmer waters of all the oceans, and none of 

 them has been found in the Polar seas. Most of them have been taken in the open ocean, 

 but they are also found swarming in harbors and other places near land. When young they 

 appear to be bottom forms, but they usually come to the surface when mature. 



I5ut little is known concerning the embryonic development of these forms. Conant, 1897, 

 found that in Tripcdalta the ovum develops into a free-swimming planula, which soon settles 

 down upon the bottom and becomes a hydra-like polyp with a mouth and 4 tentacles. Haacke, 

 1887, found a very young individual of Caryhdea rasto?iii in which a short style canal extended 

 upward from the upper floor of the central stomach to the aboral apex of the bell, and he 

 believes it possible that this structure may represent the remnant of some connection between 

 the young medusa and some form of scyphopolyp nurse, but this is wholly problematical. 



Haeckel, 1880, believed that the Carybdeidae were descended from the Stauromedusae, 

 as, according to him, were also his Periphyllidae and the Discomedusae. He believes that 

 morphologically the Carybdeidae are intermediate between the Periphyllidae and the Disco- 

 medusae. All of this, however, is speculation unsupported by a single fact of any significance. 

 We must first learn more of the early embryonic stages of the medusae of the Carybdeidae 

 and Stauromedusae before we venture to state how they may be related in philogeny to other 

 Scyphomedusae. They have perradial stomach-pouches which are partially separated by 

 interradial septa as in the Stauromedusas; indeed Goette, 1887, would consider the Caryb- 

 deidae as an ofF-shoot of or cousins of the Stauromedusae. 



Most of our knowledge of the anatomy of the Carybdeidae is due to the labors of Claus, 

 1878; Haeckel, 1880; Schewiakoff, 1889; Conant, 1898; and Berger, 1900. 



Berger, 1900, reports upon a few physiological experiments upon the reactions of Caryb- 

 deidje (see C. xaymacana). A synopsis of the genera of the Carybdeidae follows: 



(^?') Procharybdis Haechel, 1880. 4 simple pedalia. Velarium without velar canals or frenulcc. This is probably only 



a young Charyhdea. 

 Caryhdea Peron and Lesueur, 1809. 4 simple pedalia. Velarium with velar canals and with 4 perradial bracket-like 



supports (frcnula;). Stomach small, without hollow bracket-like sides arching over between it and the subumbrella. 



Stomach small and simple, with 4 horizontal clusters of gastric cirri. 

 Tamoya F. Miillcr, 1859. Similar to Charyhdea, but with a large stomach which is bound to the subumbrella by 4 



perradial, hollow arches and with 4 vertical, interradial clusters of gastric cirri. 

 Tripedalia Conant, 1897. Numerous, 8 to 12 or more, simple unbranched pedalia arranged in 4 interradial clusters. 



No hernia-like subumbrella sacs. 

 Chiropsahnus L. Agassh, 1862. 4 branched, hand-shaped pedalia with tentacles arising from the tips of the fingers. 



With 8 simple, finger-shaped, hernia-like subumbrella gastric sacs. Free-margins of the 8 gonads entire and simple. 

 Chirodropus Haeckel, 1880. Pedalia hand-shaped as in Chiropsalmus. 8 branched, hernia-like sacs projecting into 



the subumbrella from the 4 perradial stomach-pouches. Free-margins of the gonads showing grape-like swellings. 



