ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 457 



very noteworthy plasticity in the details of development, which the author 

 correlates in part with the locality from which the material came, and in 

 part with the degree of ripeness of the fertilized ova. As Richard 

 Hertwig has shown, over-ripe eggs produce a large preponderance of 

 males, and the author was able to raise the percentage to one hundred. 

 The old difficulty of a possibly differential mortality seems to have been 

 overcome. 



Development of Head in Hypogeophis.* — Harry Marcus describes 

 the development of the occipital region, of the eye-muscles and their 

 nerves, of the dorsal nerves and their ganglia, of the sympathetic and 

 the sinus cephalicus. In interpreting the architecture of the head, which 

 has a minimum of nine somites, he deals with the various sets of data 

 derived from a study of neuromeres, mesomeres, dennatoiiirivs, and 

 branchiomeres. He condenses his results, somewhat unwillingly, in a 

 provisional synoptic table of the various segments. 



Development and Evolution of Lungs. f — M. Makusckok discusses 

 the various theories : (1) that the lungs of Tetrapoda are derivable from 

 the swim-bladder of fishes ; (2) that they are organs sui generis, quite 

 independent of swim-bladder ; and (3) that they are derivable from the 

 posterior gill-pouches. 



He gives an account of what he has observed in the newt. The 

 primordia are from the first paired and bilaterally symmetrical ; they 

 appear somewhat late, and not before the fifth pair of oesophageal 

 pouches ; they present for a time a certain analogy to the fifth pair of 

 pouches. A number of details are recorded which may have a phylo- 

 genetic significance. 



Evolution-centres. J — Th. Arldt discusses critically the difficult 

 question of deciding as to the original home and headquarters of a 

 group. Among the positive criteria of importance he notes the occur- 

 rence of the oldest fossil form, of the most primitive fossil form, of the 

 majority of fossil forms, of widely distributed forms as compared with 

 local occurrence elsewhere, of primitive living forms ; and so on. 



b. Histology. 



Trophospongia and Chromidia.§ — H. Erhard has studied the so- 

 called " trophospongia " in the cells of the "bile-duct" of the snail and 

 in the epididymis of the white mouse. He makes a point of showing 

 that what Holmgren described as " trophospongia " should be called 

 chromidia. In the case of the epididymis he brings forward strong 

 evidence that it is by the activity of the chromidia in the cytoplasm 

 that the secreted substances are formed. 



Study of Chromosomes in Salamander. || — Karl Camillo Schneider 

 discusses the genesis of chromosomes in the larval salamander. Each 



* Festschrift Richard Hertwig, ii. (1910) pp. 373-462 (2 pis. and 39 figs.), 

 t Anat. Anzeig., xxxix. (1911) pp. 1-13 (6 figs.). 

 J Arch. Natur., lxxvii. (1911) pp. 211-31. 

 § Festschrift Richard Hertwig, i. (1910) pp. 133-66 (2 pis.). 

 || Tom. cit., pp. 213-32 (3 pis.). 



