zooLoay and botany, miorosoopy, etc. 219 



In the former the principal part is formed by the meso- and 

 meta-thorax ; in each segment the endosternum forms the longi- 

 tudinal axis of the floor; the flanks are sustained by three vertical 

 pieces, and the upper edge by two ; the roof of each segment 

 is formed by two parts, which are concave below, and its lateral 

 edges form an obtuse angle, oj)en below and without. The frame- 

 work of the wing is formed by six primary nervures and their rami- 

 fications, which are alternately related to the sides or the roof; the 

 general form of the wing is that of a biplanar triangle, with the base 

 centripetal and the apex centrifugal. The base is formed of an 

 anterior and a posterior plane, the latter being the more developed ; 

 the base of the wing is united to the flanks and to the roof of each 

 segment by as many articular pieces as there are nervures. The 

 apparatus of formation is constant, and may be considered as con- 

 sisting of an anterior piece, which forms a movable pivot, separated 

 by an articular cavity from the fixed pivot. The wing is able to 

 undergo torsion, thanks to the articulations of the anterior and sub- 

 anterior nervures with their basal terminations. The line of torsion 

 is a curve which passes through the basal head of the posterior 

 nervure by a special commissure, and through the basal extremity 

 of the proanterior process when it is stretched. The centrifugal 

 extremity of the wing follows in air, and during ascent, the course 

 of a sinuous line. The wing is never comparable to a simple lever ; 

 it is most nearly so in the Pseudo-Neuroptera ; the basilar pieces 

 (including the roof) may be grouped under three sides of a cone of 

 revolution, and the muscles are grouped according to these ; the 

 muscles vary greatly in direction, and it is not correct to speak of 

 exclusively vertical or horizontal muscles. 



The bat and the bird are the types of the vertebrate machine ; in 

 them the hard pieces are internal, the motors external, and this is the 

 fundamental difierence between the two types. The general form of 

 the machine, and of the wing, and the distribution of consistency to 

 the surface, as well as the rotation of the anterior edge, is comparable 

 to what is seen in insects. 



Influence of Galvanic Currents on Organisms.* — Herr L. 



Hermann has made some experiments on fourteen-day-old larva) of 

 frogs ; a current being passed through the water in which they were 

 placed, it was found that they moved, and all took up a position in 

 which the head was directed towards the anode and the tail towards 

 the cathode ; in other words, with sufficiently strong currents these 

 animals place themselves in the lines of the current, and against it. 

 If they are forced to lie with their heads towards the cathode they 

 appear to be restless. These phenomena are not observed with dead 

 larvae, and they are therefore vital phenomena. 



If the spermatozoa of frogs or mammals are placed on a slide and 

 a strong current sent through them, the head of the spermatozoon 

 turns towards the anode, but this is to be explained by purely 

 physical laws. The author makes some suggestions as to further 

 experiments on this subject. 



* Arch. f. (.1. Gesammt. Physiol. (Pfluger), xxxvii. (1885) pp. 457-60. 



