MEDUS.55. I. 



15 



Table I. Synoptic Table of the Species of Chroiiiatoncnia. 



Diameter of full-growu medusa 



Number of tentacles in full-grown medusa 



Number of cordyli between each successive pair of tentacles 



Occurrence ] 



24 — 27 mm 

 ca. 24 

 2 (0 

 Northern At- 

 lantic Ocean 



C. riibrum C. erythrogonon | C. hertwigi 

 I'ewkes Bigelow Vanhnffc-n 



38 mm 



ca. 64 



I (2) 



Eastern tropical 



Pacific 



50 mm 

 20 

 5 



Indian Ocean 



Systematical Position. — The structure of Cliroiiiato)ici)ia presents, in several regards, a 

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

 the genera Luodiced and PtycJiogena. In all of the three genera the manubrium has the same siiape: 

 the square stomach, the broad base of which is attached to the sul)umbrella 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 ChrvDiatoneiiin as in Ptychogrna 

 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 i)erradial cros.s. But 

 with regard to the structure of the gonads Clirouiatoncnin jDresents a considerable difference, not only 

 from Ptychogrna and Laodicea, but from all other Leptomedusie. As described above each of the radial 

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

 In all other Leptomedusse 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, [h. special case is the gonads of certain 

 species of Entiiiia, being transversally divided into two separated pairs 

 of gonads, one pair on the subumbrella, one jaair 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; / 

 in Ptycliogcna these pouches are much more highly developed and have 

 attained the shape of vertical lamella;, 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 onlv one gonadial band, but it is highlv folded. In 



l-ig 4. Diagrams, showing the 

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



Cliromatoiuina (a) and Plyclio- 

 more complicated. i'-wu (il. — i inner side, o outer 



side. 



The structure of the gonads of a Cliroiiiato)U)iia and a Ptycliogcna 

 may be illustrated by a diagranmiatic figure as the textfig. 4. This diagram corresponds to that b\- 

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

 Tiaridcc, viz. the Calycopsidu- and the Neoturridcr. It is not difficult to refer the two types to a common 



