ZOOLOGY AND BOTANY, ^MICROSCOPY, ETC. 295 



moi-pliic series. Intergradeg occur between mnch-ticking and little- 

 ticking. Black spotting is explained by crossing of transverse and 

 longitudinal bars. J- A. T. 



Development of Shoulder-girdle and Fore-limb in Amblystoma 

 punctatum. — S. R. Detwiler (Journ. Exper. Zool., ]918, 25, 499- 

 • 537, 33 figs.) finds that the separate parts of the shoulder-girdle 

 rudiment are already determined at the stage when the limb rudiment 

 is present as a definite thickening of the somatopleure. The removal 

 of a definite portion brings about a definite defect in the girdle. 

 Transplantation experiments show that the girdle system is not equi- 

 potential. The limb mesoderm is already determined in embryos in 

 the stage of open medullary folds. The rudiment can be successfully 

 extirpated and transplanted at this stage. J. A. T. 



Development of Fore-limb of Amblystoma punctatum. — "Ross G. 

 Haerison {Journ. Exper. ZooL, 1918, 25, 413-01, 45 figs.) finds that 

 the fore-limb arises from a group of mesoderm cells formed as a pro- 

 liferation of the somatopleure. It is a self-diff"erentiating system. No 

 specific stimulus from any particular part of the ectoderm is neces- 

 sary for its development. The rudiment is not to be regarded as a 

 definitely circumscribed area, like a stone in a mosaic, but as a centre 

 of differentiation in which the intensity gradually diminishes centri- 

 fugally. It is an cquipotential system, for Harrison's experiments 

 show that a whole will develop from a part, and a single normal whole 

 will develop out of two separate rudiments fused together. " The limb 

 rudiment, therefore, is an entity, which, except for its dependence for 

 nourishment, is independent of its siuToundings in the attainment of its 

 specific form." J- A. T. 



Regeneration after Exarticulation in Diemyctylus viridescens. 

 — C. V. Morrill {Journ. Exper. Zool, 1918, 25, 107-33, 3 pis.) has 

 experimented with this American salamander, and finds that regenera- 

 tion takes place readily after complete extirpation at hip, knee, or 

 ankle joint. The new skeletal elements are like the old. The new 

 cartilage appears independently (1) around the shaft of the bone 

 proximal to the epiphysis (and this peripheral cartilage is of periosteal 

 orio-in) ; (2) in the axis of the bone and in contact with the marrow 

 subsequent to detachment of the epiphysis (and this axial cartilage arises 

 from cells of the old epiphyseal cartilage and from the endosteal hning 

 of the marrow cavity) ; and (3) in the tissue of the bud distal to the 

 epiphysis (and this embryonal cartilage arises from de -differentiation 

 leading to a substratum of indifferent cells). The removal of single 

 bones was studied. J- A. T. 



Effect of Starvation on Tadpoles. — W. W. Swingle {Journ. Exper^ 

 Zool., 1918, 24, 545-G5, 14 figs.) finds that total starvation inhibits 

 indefinitely the growth and metamorphosis of larval frogs. It prevents 

 the development of the germ-glands and delays any increase in the 



