260 SUMMARY OF CURRENT RESEARCHES RELATING TO 



straight canals. The state of affairs is similar to that described by 

 Portmaim in gninea-pig, dog, Torpedo and Myliohatls aquila. J. A. T. 



Endolymphatic Organ of Batrachians. — -Georges Portmann 

 {Comptes Rendus Soc. Biol, 1921, 84, 13;]-6, 1 fig.)- The endolym- 

 phatic organ of frog and toad consists of an intra-cranial sac of con- 

 siderable size and of a short wide Canal connecting the sac with the 

 saccule. Moreover the endolymphatic sac gives origin to a postero- 

 external diverticulum which traverses the cranial wall and comes into 

 intimate contact with the lagena. Contrary to what the author has 

 found to be the case in mammals and birds, the endolymphatic sac 

 of Batrachians is quite surrounded by the arachnoid spaces. As in 

 Selachians, birds and mammals, so in Batrachians ; the endolymphatic 

 sac does not communicate with the utriculus except by the intermedia- 

 tion of the sacculus. J- A. T. 



Scales of Twait Shad as Indices of Growth. — Louis Roule 

 (Gomptes Rendus >Soc. Biol, 11»20, 83, 1542-4). From readings of the 

 markings of the scale of this fish (Glvpea or Alosa finta), it is concluded 

 that there are two annual periods, a period of summer growth and a 

 period of winter arrest. This alternation is marked by the rings on the 

 scales. It is also shown that the males are smaller than the females, 

 and are able to reproduce when two or three years old, whereas the 

 females are reproductive from the third to the fifth year inclusive. 



study of Yellow Perch. — A. S. Pearse and Henrietta Achten- 

 BERG (^Bidl Bureau Fisheries Washington, 1920, 36, 279-366, 1 pi., 

 35 figs.) The yellow perch {Perca ffavescens), studied in Wisconsin 

 lakes, is a versatile feeder, the favourite items being Chironomid larv«, 

 Cladocera, Corethra and other larv^, fish, amphipods and debris. There 

 are marked seasonal difPerences, and in general the favourite foods are eaten 

 in proportion to abundance and availability. An adult perch eats about 

 7 p.c. of its own weight in a day. Digestion is three times more rapid in 

 summer than in winter. Food varies with age. During youth there is 

 a change from Cyclops and other Entomostraca to Hyalella and insect 

 larvfB. At the end of the first season the food is much like that of the 

 adults. Perch may remain in oxygen-free water for two hours without 

 dying. When in water without oxygen they use part of the oxygen in 

 the swim-bladder. Perch may become sexually mature in two years. 

 Except during the spawning (in shallow water) most of the perch in the 

 large lake remain in deep water. There appears to be an upward move- 

 ment at night. They usually swim in school and move about. Pickerel 

 and Lota macidosa are important enemies. Small lakes have fewer 

 perch mainly because of the shallowness and exposure. J. A. T. 



Neuromerism and Metamerism in Dogfish. — P. Wintrebert 

 {Comptes Rendus Soc. Biol, 1921, 84, 191-4). The head of the embryo 

 of Squalus acanthias shows obvious neuromeres, but it is difficult to 

 correlate these with the metameres of the head. J. A. T. 



