DEVELOrMENT OF THE TADPOLE. 73 



Fig. 3. — Horizontal median section of same, same date : ep., epiblast ; 

 mf., mesoblast ; c, body cavity ; b., brain ; nc,, neural cavity. 

 ,, 4, 5. — Oblique sections of same through the head portion taking 

 in part of the yelk mass ; mp , muscle plate ; no. , notochord ; 

 sno., sub-notochordal rod ; pr., pro-renal duct, other letters 

 as before. 



Plate VIII. 



Fig. 1. — Vertical longitudinal section, March 9 : 6r., brain ; tdc, noto- 

 . chord; c7., claspers ; s., somites; c, body cavity; y., yelk 



mass. 

 ,, 2. — Vertical longitudinal section, March 11. ^^rd. , pericardium, 



with immature heart. 

 ,, 3. — Longitudinal horizontal section of same; an., au. (marked 



ace. on plate), auditory capsule; 2:)ni, pro-renal ducts; 



g., gills ; hr., brain. 

 ,, 4. — Longitudinal horizontal section through, nfc. , notochord, 



March 12. Other letters the same. 



The Phosphorescent Light of Glow-Worms. — From the 

 curious experiment mentioned in one of the late numbers of the 

 Alonitcur de la Photograplue, in which a glow-worm acted, by the 

 light emanating from its body, on a gelatine-bromide plate placed 

 at the bottom of a darkened box, this light appears to be about 

 uf tlie same actinic intensity as the phosphorescent light of sul- 

 phuret of calcium. It appears that the light of glow-worms and 

 of all phosphorescent animals is caused by a substance called 

 noctilucine, which is secreted by the animal as it is used, and that 

 the light is due to the slow oxidation of this substance. If some 

 of these insects have been seen to retain their luminosity in a 

 vacuum, or in hydrogen gas, it is because their tissue always 

 contains enough oxygen to allow the slow oxidation of the nocti- 

 lucine to continue under the circumstances for a certain length of 

 time. 



Instinct of Birds. — It is reported in Peru and other parts of 

 South America, last year's fruit has been avoided by birds, while it 

 has caused the death of sheep and cattle when fed on them in 

 large quantities. These observations have been cited as tending 

 to show that the instinct of birds, with respect to the wholesome- 

 ness of fruits, is frequently a worthy guide for human beings to 

 follow. The possibility is suggested that the variation in the 

 fruit of different years may have something to do with the out- 

 break of cholera. 



