2. _Aeginidae._--Radii a multiple of four, with radial gastric pouches bifurcated or subdivided; the tentacles are implanted in the notch between the two subdivisions of each (primary) gastric pouch, hence the (secondary) gastric pouches appear to be "internemal" in position, i.e. to alternate in position with the tentacles. _Aegina_, with four tentacles and eight pouches; _Aeginura_ (fig. 25), with eight tentacles and sixteen pouches; _Solmundella_ (fig. 67), with two tentacles and eight pouches; _Aeginopsis_ (fig. 23), with two or four tentacles and sixteen pouches. 3. _Solmaridae._--No gastric pouches; the numerous tentacles arise direct from the stomach, into which also the peronial canals open, so that the ring-canal is cut up into separate festoons. _Solmaris_, _Pegantha_, _Polyxenia_, &c. To this family should be referred, probably, the genus _Hydroctena_, described by C. Dawydov [11a] and regarded by him as intermediate between Hydromedusae and Ctenophora. See O. Maas [35]. _Appendix to the Trachylinae._ Of doubtful position, but commonly referred to the Trachylinae, are the two genera of fresh-water medusae, _Limnocodium_ and _Limnocnida_. _Limnocodium sowerbyi_ was first discovered in the _Victoria regia_ tank in the Botanic Gardens, Regent's Park, London. Since then it has been discovered in other botanic gardens in various parts of Europe, its two most recent appearances being at Lyons (1901) and Munich (1905), occurring always in tanks in which the _Victoria regia_ is cultivated, a fact which indicates that tropical South America is its original habitat. In the same tanks a small hydroid, very similar to _Microhydra_, has been found, which bears medusa-buds and is probably the stock from which the medusa is budded. It is a remarkable fact that all specimens of _Limnocodium_ hitherto seen have been males; it may be inferred from this either that only one polyp-stock has been introduced into Europe, from which all the medusae seen hitherto have been budded, or perhaps that the female medusa is a sessile gonophore, as in _Pennaria_. The male gonads are carried on the radial canals. _Limnocnida tanganyicae_ was discovered first in Lake Tanganyika, but has since been discovered also in Lake Victoria and in the river Niger. It differs from _Limnocodium_ in having practically no manubrium but a wide mouth two-thirds the diameter of the umbrella across. It buds medusae from the margin of the mouth in May and June, and in August and September the gonads are formed in the place where the buds arose. The hydroid phase, if any, is not known.