11EF0RT ON THE DEEP-SEA MEDUSAE. 47 



goes retrograde formation at the same time, the former originate the characteristic 

 internemal gastral pouches of the iEginidae, which were primarily placed in pairs between 

 every two tentacles (as in the tetranemal /Egina, System, 1879, p. 337, taf. xx.). The 

 two pouches which have a tentacle between them are therefore the distal halves belong- 

 ing to a former pernemal gastral pouch, i.e., of a radial canal at the end of which each 

 tentacle was originally placed. But the two pouches lying between every two primary 

 tentacles are opposite distal halves of two adjacent radial canals. This view is justified 

 by the fact, that in all the older and simpler forms of the iEginidse two gastral pouches 

 are always placed between every two tentacles. In our JEginura (as in AZginopsis) each 

 of the eight lobe pouches is divided a second time. The peculiar formation of the 

 festoon canals of the iEginidse can only be explained in this way. It shows essentially 

 the same conditions as in the Cunanthidge. Here as there, the originally simple 

 circular canal is divided into the same number of separate arches or " lobe canals " as 

 there are umbrella lobes, and each lobe canal opens with two mouths beside the base 

 of two neighbouring canals. But whilst in the Cunanthidse the opening of the lobe canal 

 is found in the middle of the distal margin, in the iEginidse it occurs immediately in 

 the periphery of the stomach. In the former the undivided proximal part or principal 

 part of the radial canals (or of the pernemal gastral pouches) has entirely disappeared, and 

 the internemal lobe pouches only are left (as remains of the divided distal part). The 

 inverted halves of every two adjacent lobe canals are also connected with a " double 

 canal" or double " peronial canal." In the iEginidse, as the proximal half of the 

 umbrella margin has retrograded, and the distal half become proportionally more strongly 

 developed, the double canal appears very much prolonged, and has the deceptive 

 appearance of " a simple radial canal opening into the periphery of the stomach 

 between every two internemal gastral pouches." Thus very simple and clear homologies 

 exist between formations apparently very different, as I have already shown in my 

 System der Medusen, 1879, pp. 305, 306, &c. 



The specimen of ^Eginura myosura was a male, and its sixteen testes (the sixteen 

 "internemal gastral pouches") contained masses of ripe spermatoza. They did not however, 

 fill up the cavity of the pouches, but were placed on the outside of its subumbral wall. 

 In transverse sections the internal side of the subumbral wall showed the same high 

 cylindrical epithelium as that of the peronial canals (figs. 7, 12), whilst the endodermal 

 epithelium of the opposite umbral wall consisted, in both cases, of a thin layer of flat 

 plate cells covering the gelatinous substance of the umbrella. The spermarium, 

 on the contrary, lies like a thick plate immediately under the exoderm epithelium 

 of the subumbrella from which it originates, and is divided from the high cylindrical 

 epithelium of the endoderm by a distinct supporting plate. In jEginura as in 

 Pegantha (p. 34, PI. XL figs. 5, 6), the subumbral ectoderm sends out supporting fibres 

 containing nuclei into the spermarium which lies under it, and is derived from it. Here, 



