HARDWICKE'S SCIENCE-GOSSIP. 



6i 



food, being surrounded by a thick serrated lip, within 

 and upon which are several rows of black spines 

 pointing to the triangular mouth also fringed with 

 them. On April 15th, the blue filmy specks had 

 become perfect eyes ; from this time until May loth 

 no great change took place beyond increased size 

 and activity. Their bodies were beautifully speckled 

 with a golden-yellow colour, and the black pigment 

 cells assumed an irregular stellate form. 



The membranous sheaths were now projected from 

 each side of the tail near the body, through which 

 the posterior limbs are pushed. These appeared 

 ten days later, and from their extreme transparency, 



is suddenly broken through, and the limbs at once 

 become exposed. 



In some young toads undergoing metamorphosis 

 at the same time, the action of the fore-limbs could 

 be seen through the translucent skin, moving in 

 unison with those posterior, and ultimately emerging 

 as with the frog. 



When furnished with fore-limbs, they endeavour 

 to leave the water and rest upon the a([uatic plants 

 on the surface. If compelled to remain in deep 

 water they soon become asphyxiated. 



The perfect frog is developed somewhat suddenly 

 at the end of its metamorphosis. The tadpole tail 



Fig. SI.— Dorsal aspect of Tadpole, nat. size and magnified 

 (seventeenth day). In this figure and 52, a shows external 

 gills ; b, nostril ; c, rudimentary mouth having rapid ciliary 

 action. 



Fig. 52. — Dorsal aspect of Tadpole (twentieth day) magnified ; 

 d, first appearance of membranous sheath through which the 

 posterior limbs protrude. 



Fig. 53.— Lobe of external gill (magnified) showing 

 ^ circulation of Llood (twentieth day). 



together with the tail and margin of the body, ex- 

 hibited the blood circulation to perfection. 



I found that the tadpoles lie quietly enough for 

 examination upon a glass slide when partially covered 

 with wet cotton-wool ; this saves the compression 

 and probable destruction of the object. 



Tadpole vigour and activity increased with the 

 warmth of June. They frequently breathed from 

 the surface, and now used their limbs in swimming. 

 Those anterior began to bud (the toes had been 

 previously remarked beneath the cuticle), but unlike 

 the posterior limbs are not protruded through a 

 membranous sheath ; they elbow their way out be- 

 neath the gill openings ; the attenuated integument 



Fig. 54.— External gill (magnified), March 23rd. 



assumes an extreme length and tenuity, then it as 

 quickly becomes absorbed together with the lips and 

 secondary gills, and finally, the body is shrunk to a 

 frog shape. 



Some of my captives completed their wonderful 

 series of life-changes and became lung-breathing 

 batrachians on June 27th, thus occupying one hundred 

 and seventeen days \\\ their development from the 

 deposition of the spawn. A warmer and more equable 

 temperature would, I think, have accelerated the 

 process. Light appears principally necessary as a 

 stimulus to the growth of vegetation and production 

 of Infusoria, upon which they seemed chiefly to subsist. 

 Any animal food put beside them was usually 



