ATLANT. DEEP-SEA EXPED. 1910. VOL. III.] 



ANTHOMEDUSAF. AND LEPTOMEDUSAE. 



both cirri and cordyli. Only a few cirri were present in 

 his specimens; they are cylindrical and provided with a 

 cluster of nematocysts in the distal end. The cordyli are 

 spindle-shaped and carry no nematocysts. One or two 

 cordyli are present between every two successive ten- 

 tacles. These cordyli are undoubtedly homologous with 

 the small marginal appendages of Chromatonema rubrum. 

 The two species are undoubtedly nearly related; in fact, 

 I can see no other noticeable differences than the want 

 of nematocysts in the cordyli of "Ptychogena" erythrogonon, 

 and the size, Chromatonema rubmm reaching maturity 

 when about 24 mm. in diameter with about 24 tentacles, 

 whereas Chromatonema erythrogonon grows to a larger 

 size and may possess 64 tentacles when fully developed. 



Another similar form is described by Vanhoffen 

 (1911) as Ptychogena Hertwigi, found in the Indian Ocean 

 by the German deep-sea expedition. Vanhoffen describes 

 his species as very like Pt. erythrogonon Bigelow, but 

 still larger, 50 mm. in diameter, yet with a smaller number 

 of tentacles, viz 20. Cordyli are said to be wanting, 

 but there are 5 "cirri" between each successive pair 

 of tentacles. These "cirri", as shown in the figure in 

 the text, seem to be partly cylindrical, partly somewhat 

 club-shaped, partly spindle-shaped. They are, thus, un- 

 doubtedly homologous with the cordyli of Chromatonema 

 rubmm and erythrogonon. According to the coloured 

 figure (Taf. XXII) the gonads reach to the middle of 

 the radial canals. — Also this species is undoubtedly nearly 

 related to Chromatonema rubmm Fewkes and belongs 

 to the same genus. 



Further investigations will show, whether the three 

 species mentioned above are distinct or only local varieties 

 of one species, viz, Chromatonema rubmm Fewkes. 



Synoptic Table of the Species of Chromatonema. 



Diameter of full-grown 

 medusa 



Number of tentacles in 

 full-grown medusa 



Number of cordyli between 

 each successive pair of 

 tentacles 



Occurrence J 



C. rubrum 

 Fewkes 



24—27 mm. 

 ca. 24 



2 (1) 



Northern At- 

 lantic Ocean 



C. erythro- 

 gonon 

 Bigelow 



C. hertwigi 

 Vanhoffen 



38 mm. 

 ca. 64 



1 (2) 



Eastern tropi 



cal Pacific 



50 mm. 



20 



5 

 Indian Ocean 



Systematic position. — Fewkes (1882) who first 

 described this species, called it by the preliminary name 

 Chromatonema rubrum until its systematic position could 



be stated ; he added that it was "apparently allied to 

 Staurophora" . — Mayer (1910) referred it to the genus 

 lhaumantias, because it is a Leptomedusa with several 

 tentacles but without otocysts, ocelli and cordyli. In my 

 paper of 1913 I followed him in this respect. — The medusa 

 described by Bigelow (1909) and mentioned above, was 

 referred by him to the genus Ptychogena owing to the 

 presence of "lateral diverticula" from the radial canals 

 and of "cordyli" between the tentacles. Also the medusa 

 described by Vanhoffen (1911) was referred to the 

 genus Ptychogena. 



As a matter of fact, the genus Chromatonema bears 

 a considerable likeness to various members of the family 

 Laodiceidae. With regard to the general shape of the 

 gastro-genital system Chromatonema is very like Laodicea 

 and Ptychogena. In the latter genera, it is true, each of 

 the radial canals bears only two lateral gonads, more or 

 less folded, whereas in Chromatonema there are two rows 

 of completely separated, sack-shaped gonads. It is not 

 difficult, however, to refer these two types of gonads to 

 a common origin, and they do not contradict the sup- 

 position of a phylogenetic relationship. They recall the 

 typical structures of the gonads in the two main-groups 

 of Tiaridae, viz. Neoturridae and Calycopsldae, as pic- 

 tured by Hartlaub (1913, fig. 295, p. 347). 



The most characteristic feature of the Laodiceidae 

 is the possession of cordyli. A typical cordylus is club- 

 shaped and destitute of nematocysts. We know, however, 

 cordyli in which the club-shape is not pronounced, and 

 in Ptychogena antarctica Browne (1910) has observed 

 nematocysts in some of the cordyli. These cordyli esta- 

 blish a transition from the typical cordyli to the small 

 marginal appendages of Chromatonema. The structure 

 and arrangement of the cell-layers in the latter are exactly 

 as in a cordylus, the entoderm, consisting of cubical cells, 

 surrounding a central lumen communicating with the circular 

 vessel. This fact distinguishes the cordyli from the cirri, 

 which are solid, the entoderm consisting of a single row 

 of cells. I do not hesitate, therefore, to call the small 

 marginal appendages of Chromatonema with the name 

 of cordyli. Altogether, I have no doubt but that the 

 genus Chromatonema has to be included into the family 

 Laodiceidae. On the other hand, the shape of the gonadial 

 system in Chromatonema has a great likeness to that 

 structure in certain species of the Tiaridae among the 

 Anthomedusae, especially Catycopsis which has 8 adradial 

 rows of sack-shaped gonads, projecting inwards into the 

 stomach and visible on the outer surface of this as rows 

 of transverse fissures. Besides, the cordyli of Chromato- 

 nema bear a great likeness to the dwarf-tentacles of 

 Tiaranna rotunda. — Altogether, Chromatonema belongs 

 to the family Laodiceidae, and within this group it is the 



