MEDUSA. I. 



Table I. Synoptic Table of the Species of Chromatonema. 



Systematical Position. The structure of Chromatonema presents, in several regards, a 

 considerable resemblance to the members of the family Laodiceid previously known, particularly to 

 the genera Laodicea and Ptychogena. In all of the three genera the manubrium has the same shape: 

 the square stomach, the broad base of which is attached to the subumbrella along the arms of a 

 perradial cross; the short, wide mouth-tube, and the folded mouth-edge, in the four corners of which 

 lips are just indicated. Common for the three genera is, moreover, the structure of the four radial 

 canals; the proximal part of each of the canals contains the gonads; the ventral part of this gonadial 

 part is funnel-shaped and is the proper digestive part of the canal. In Chromatonema as in Ptychogena 

 the dorsal line of attachment of the radial canal to the subumbrella is pinnate, and in older individu- 

 als of all of the three genera the proximal part of the gonads may be developed within the corners 

 of the stomach in the dorsal wall of the latter on both sides of the arms of the perradial cross. But 

 with regard to the structure of the gonads Chromatonema presents a considerable difference, not only 

 from Ptychogena and Laodicea, but from all other Leptomedusse. As described above each of the radial 

 canals in Chromatonema carries two rows of sack-shaped gonads, completely independent of one another. 

 In all other Leptomedusae each radial canal bears either two lateral gonads, forming two continuous 

 masses in the ectoderm of a certain part of the lateral walls of the canal, or only one gonad com- 

 pletely surrounding a shorter or longer part of the canal. (A special case is the gonads of certain 

 species of Eutima, being transversally divided into two separated pairs 

 of gonads, one pair on the subumbrella, one pair on the stomachal peduncle). 

 In some forms the gonadial bands are straight and linear, in others they 

 are more or less undulated or folded. In Laodicea the lateral walls of the 

 gonadial parts of the radial canals have a number of short lateral pouches; f 

 in Ptychogena these pouches are much more highly developed and have 

 attained the shape of vertical lamellae, the dorsal edges of which are atta- 

 ched to the subumbrella; but still there is only one gonad on each side of 



the canal; there is only one gonadial band, but it is highly folded. In 



Fig 4. Diagrams, showing the 

 Staurophora the gonads have a similar structure, but the folding is still structure of the gonads of 



Chromatonema (a) and Ptycho- 

 more complicated. gena (6J. i inner side, o outer 



side. 

 The structure of the gonads of a Chromatonema and a Ptychogena 



may be illustrated by a diagrammatic figure as the textfig. 4. This diagram corresponds to that by 

 which Hartlaub (1914, p. 347) illustrates the typical folding of the gonads in the two groups of 

 Tiarida, viz. the Calycopsidce and the Neoturrida. It is not difficult to refer the two types to a common 



