6o 



HARDWICKE'S SCIENCE-GOSSIP. 



tail grew rapidly ; the nostril became conspicuous, and 

 on the fourteenth day (March 17th) a rapid energetic 

 motion (the embryo bringing head and tail together 

 ■with a'jerk) was first observed. Figure 49 A, enlarged 

 at B. The next day a few tadpoles had emerged and 

 were lying upon the gelatinous egg mass cccasionally 

 indulging in a vigorous wriggle. This action seemed 

 to clear them of the albuminous investing globule 

 upon the debris of which they continued to lie and 

 probably feed until its disappearance. 



the protuberance c (the immature mouth), from 

 which, judging by the movement of floating particles, 

 the water was driven backward in a current to the 

 gills. The smaller figures represent the dorsal aspect 

 at this stage. 



Figure 52 represents the tadpole on the twentieth 

 day. The gills now extended almost to the tail, and 

 the membranous sheaths through which the posterior 

 limbs protrude were plainly visible through the trans- 

 parent cuticle at d. 



Fig. 44. — Frog Spawn in siiii. March 3rd. "] 



Fig 4s.— Cleavage or segmentation of Eggs. 

 March 8th (fifth day). 



^p/ Fig. 47. — Cleavage or segmentation ] 

 of Egg (eighth day). », i 



Fig. 46.— Cleavage or segmentation of 

 '. Eggs (sixth day). 



Fig. 48. — Cleavage or segmentation of Eggs 

 (ninth day). 



Fig. 49. — Segmentation of Egg (fourteenth day) 

 B, enlarged. 



Fig. 50. — Tadpole emerged (sixteenth day) ; 

 length j'j inch. Right-hand figure magni- 

 fied 3 times. 



Figure 50 i-epresents the appearance of a tadpole 

 after emergence, its length being 7a n\d\, together 

 with an example magnified about three diameters. 



A vigorous circulation passed through the gills 

 (a fig. 51 magnified about eight diameters). On the 

 seventeenth day (March 20th) these had increased in 

 volume and were prettily branched under a one-inch 

 objective, the membranous sides of the tail appeared 

 speckled with pigment cells ; the nostrils l> were well 

 developed and a rapid ciliary action was ajiparent at 



Cold weather now intervened, and during its- 

 continuance tadpole development was arrested. The 

 first important change occurred on April 5th, when, 

 the eyes could be distinguished only, however, as 

 bluish filmy specks, far too rudimentary for distinct 

 vision. The weather having become warmer, growth 

 went steadily on ; the external gills became absorbed, 

 and they now breathed by the secondary or internal 

 gills fish-like. The mouth seems adapted to exert a 

 scraping as well as a sucking action upon the animal' s- 



