254 SUMMAEY OF CUREENT EESEARCHES RELATING TO 



frog, those of Sahno and Osmeriis develop iu a physiological salt solution 

 isotonic with the adult animal. Oviducal eggs of Sahno have the same 

 osmotic pressure as the blood of the adult. Fertilized eggs have an 

 osmotic pressure only a little lower than that of the oviducal eggs. An 

 isotonic salt solution greatly delays the disorganization of the cell-plasm 

 which occurs in fresh water. A thickening of the egg-membrane occurs 

 after contact with fresli water or distilled water. This does not occur in 

 Ringer's solution. In Einger's solution the eggs retain for at least three 

 days their capacity of being fertilized. The principal planes of the 

 embryo are pre-determined in the unfertilized egg. The larvae of 

 S. salvelinus are permeable for potassium chloride. The egg-membrane 

 greatly slows the diffusion of electrolytes. J. A. T. 



Transplantation of Limbs in Amblystoma. — Ross G. Harrison 

 {Journ. Exper. Zool, 1921, 32, 1-136, 136 figs.). Experiments with 

 the fore-limb bud of Amblystoma punctatum, transplanted in various 

 ways. In various stages of development the transplanted buds grow 

 out in the direction of what was originally the posterior pole of the antero- 

 posterior axis. The asymmetry of the new limb is determined by two 

 factors, the polarization of the antero-posterior axis of the limb-bud, and 

 the orientation of the limb-bud with respect to the dorso-ventral polariza- 

 tion of its organic environment. Duplex and multiplex limbs frequently 

 arise from the transplanted buds. Limbs placed in abnormal places, 

 where the specific blood and nerve supply is lacking, are frequently 

 resorbed or are functionless or imperfectly functional if they do develop. 

 There are some regulative phenomena. The limb-bud is an equi- 

 potential system. Except for the circumstance that the dorso-ventral 

 differentiation of the limb-bud is a function of the orientation of the 

 bud with respect to its organic environment, the limb-bud is a highly 

 specific self -differentiating system. Its definitive form must, therefore, 

 be represented in the organic elements (intimate structure) of the limb 

 rudiment. One quality of these elements is their polarization. The 

 transplanted limbs show both regulation of form and functional adapta- 

 tion, but these do not necessarily go hand in hand. J. A. T. 



Influence of Nerve on Taste-cells and Regeneration in Amiurus. 

 —J. M. D. Olmsted {Journ. Exper. Zool, 1020, 31, 369-401, 4 pis.). 

 The taste buds on the barbels of this fish are composed of one kind of 

 cell, sense-cells, between which lie nerve fibres. The small leucocytes 

 and larger wandering pigment cells included in the buds are different 

 stages of the same phagocytic cell, which is extruded from the surface of 

 the skin when filled with waste material. Within eleven to thirteen days 

 after cutting the branches of the seventh nerve leading bo the barbels, the 

 taste buds disappear. They degenerate, are phagocytized, and replaced 

 by indifferent epithelial cells. About the eighteenth day the nerve 

 begins to regenerate at the base of the barbel ; the taste buds begin to 

 reappear ; by the end of forty days the restoration is complete. New 

 barbels regenerate where old ones are removed, and become fully 

 equipped with taste buds. Barbels whose nerves have been cut do not 



