32 SUMMARY OF QUERENT RESEARCHES RELATING TO 



takes place in the acid solution. In stronger acid, ho^vever, recovery 

 only takes place on removing the gills to a more alkahne solution. In 

 still stronger acid the cells become opaque and are killed. Mussel gills 

 exposed to an abnormally high concentration of hydroxyl ions behave in 

 a remarkable ^^'ay. In such solutions the ciliary action is either not 

 affected at all or proceeds at an abnormally rapid rate, but the individual 

 cells of the ciliated epithelia break away from each other and move 

 about in the solution owing to the movement of their cilia. A number 

 of experiments show that sodium, potassium, calcium, and magnesium 

 are all necessary to maintain gill fragments in a normal state of ciliary 

 activity for a protracted period, viz. four days. If one or more metals 

 are omitted, the individual cells of the ciliated epithelia show the same 

 disruptive phenomenon as in sea-water of abnormally high concentration 

 of hydroxyl ions. J. A. T. 



c. General. 



Comparative Study of Rodent Brains. — L. Eeisixger {ZooL 

 Anzeiijer, 1920, 51, 107-1), 4 figs.). A comparison of the brains of 

 rabbit, squirrel, rat, and guinea-pig, which show close similarity, although 

 the animals differ much in apparent intelligence. There is certainly no 

 close correlation between convolutions and intelligence. The point is 

 made that if there is sufficient cranial space there is no need for con- 

 volutions. Many small rodents may have a relatively large brain, 

 though this is- almost smooth. J. A. T. 



Variations of Pit Viper. — Joan B. Procter {Proc. ZooL Soc, 

 11)18, 163-82, 5 figs.). An account of the variation of the principal 

 characters of the Central and South American pit viper, Lachesis atrox. 

 With this species L. lanceolatus is synonymous, and of this species 

 L. affinis Gray, L. jararaca Wied., and L. jararacussu Lacerda are 

 varieties. The more northern form L. affinis is most primitive in its 

 markings, and from it the patterns of the markings of the others may 

 be derived. J. A. T. 



The Urodele Vomer. — Inez Whipple Wilder [Proc. Amer. Soc. 

 Zool. in Anat. Record, 1920, 17, 349). A study of the vomer in SpeUrpes, 

 Diemyctylus, and Amhlystoma. During the metamorphosis in Spelerpes 

 the vomer shows (1) an anterior and lateral extension as a plate-like 

 reinforcement of the floor of the nasal region ; (2) an extension of the 

 median part, mainly in a posterior direction, through the fusion of the 

 bases of a new series of teeth which appear at this time in the roof of 

 the mouth ; and (3) the absorption of the larval vomerine teeth of the 

 ridges that bore them, so that this region also becomes thin and plate- 

 like. J. A. T. 



Pectoral Fin of Eusthenopteron. — Branislav Petronievics {Ann. 

 Mag. Nat. Hist., 1918, 2, 471-6, 2 figs.). A description of the skeletal 

 structure of this fossil fish and a discussion of its homology with the 

 tetrapod limb. The posterior bifurcation of the fourth axonost may be 

 a remnant of a more primitive stage in which the fourth axonost was 



