;;.-, | SUMMAR? OF CURRENT RESEARCHES RELATING TO 



R. tigrina remains active throughout the year. It is distinguished by 

 the following characters : The snout is less pointed than in II. tigrina 

 and does no! projecl so far beyond the mouth, the tibio-tarsaJ joint falls 

 short of the car. the internal metatarsal tubercle is feebly developed, 

 and the skin of the back is more warty than in the allied species. The 

 dorsal surface is of a dull brownish colour spotted with black, the ventral 

 surface also marked with black sometimes in a reticulate pattern. 



Electric Eels.* — CI. Schlesinger points out that the Gymnonoti 



include two entirely distinct families, the eel-shaped Electrophoridae and 

 the laterally compressed Gymnonotidae. The latter are derived from a 

 common primitive stock which has diverged upon three lines, the primi- 

 tive Giton, the Sternarchinae (with dorsal filament and caudal fin), and 

 the Gymnotinas (without dorsal filament and caudal fin). There is a 

 very striking parallelism and convergence between Gymnonoti and 

 Mormyridae, showing how similar conditions evoke similar results. The 

 author shows that the characteristic mode of locomotion in Electrophorus 

 —solely by undulations of the anal fin while the body is kept stiff — 

 occurs in the Gyninotidas. In another interesting paper t he concludes 

 that the same is true of the Xotopteridae. 



Study of Species of Gadus.J — Louis Fage has made a rather in- 

 teresting study of Gadus luscus Linne, G. capelanus (Risso), and 

 G. minutus 0. Fr. Miiller. He first shows that the three species are 

 distinct. He then considers the phylogenetic value of the differentiating 

 characters, and finds that the three species may be ranked in a phyletic 

 series illustrating progressive adaptation to nektic life, G. capelanus being 

 intermediate between the less evolved G. luscus and the more evolved 

 G. minutus. 



Synopsis of Lampreys. § — C. Tate Regan has prepared a synopsis of 

 the order Hyperoartii. He gives the following definition : Marsipo- 

 branchs with the nasal aperture on the upper surface of the head and 

 the naso-palatine canal ending blindly posteriorly. Eyes well developed 

 (in the adult). Two semicircular canals. Mouth with expanded toothed 

 lips ; tongue with a single anterior, and a pair of posterior cuspidate 

 lamina (compound teeth). Branchial sacs seven on each side, not far 

 behind the head, communicating internally with a subcesophageal canal 

 which opens anteriorly into the pharynx ; an extra-branchial skeleton 

 forming a basket-work. Eggs small, numerous; segmentation holo- 

 blastic ; a metamorphosis. A caudal and two dorsal fins, sometimes 

 united. 



The larvae (Ammoccetes) appear to be extremely similar in all the 

 northern genera. They are toothless, with a small transverse lower lip 

 and a hood-like upper lip ; a circle of fringed barbels surrounds the 

 month. The eyes are rudimentary and subcutaneous, the small gill- 

 openings lie in a groove and the vertical fins are confluent. The 

 branchial pouches communicate directly with the oesophagus. 



Eight genera are recognized — Mordacia, Geotria, Petromyzon, Ichthyo- 

 myzon, Gaspiomyzon, Eudontomyzon g. n., Entospheims, and Lampetra. 



* Zool. Jahrb., xxix. (1910) pp. 613-40 ( 3 pis. and 4 figs.). 



t Tom. cit., pp. 681-8 (1 pi). 



X Arch. Zool. Expeu., vi. (1911) pp. 257-82 (2 pis.). 



§ Ann. Nat. Hist., vii. (1911) pp. 193-204. 



