Ixxxviii GENERAL SUMMARY OF SCIENTIFIC AND 



Birds. It belongs to an intermediate type, which must take 

 its place below that of the two classes just mentioned, and 

 above that of the Batrachians. 



Some observations on the mode of walking of the Arma- 

 dillos have been made by Mr. Bartlett, of the London Zo- 

 ological Gardens. He observes that two species of Chceto- 

 2)hractus walk on the tips of their toes, like species of Xenu- 

 riis, while certain other forms, as Eiqyhractics, a member of 

 the same family, and three species of another family, the 

 TatusiadcB^ walk on the palms of the forefeet, with the claws 

 spread out, and the tips elevated from the soil. 



Of the physiological laws governing the size of the indi- 

 vidual, we know comparatively little. The matter may be 

 approached by a study of the changes in size and weight of 

 insects while passing tlirough their m.etamorj^hoses, for virt- 

 ually the larva of an insect is a difierent animal from the 

 pupa or chrysalis, differing anatomically and in its habits ; 

 so with the imago or adult, as compared with the chrysalis. 

 The experiments of the distinguished English anatomist and 

 physiologist, Newport, had shown that in the pupal state res- 

 piration still goes on, though to a diminished extent, so that 

 the carbonic acid and water excreted by the pupa, being un- 

 compensated by food, must be a dead loss of matter to the 

 insect. As preliminary to the study of this subject, Mr. 

 Meldola has published in the Annals and Magazine of Nat- 

 ural History an article in which he confirms Newport's state- 

 ment that there is a loss of substance in the pupal state. He 

 also finds that this loss is different in amount in individuals 

 of the same species exposed to the same temperature, and 

 that it is less in amount than that occurrina: in the same 

 species in the perfect state or in a dead pupa by desiccation 

 the comparisons extending in all cases over equal periods of 

 time. They prove also, he adds, what is far more important 

 to our present inquiry, that the variation in loss is sufficient 

 in amount to lead us to expect the size, or at least the specific 

 gravity, of the imago to be sensibly influenced by it. 



Of kindred interest are certain inquiries which occasionally 

 come up as to the mode of production of sex. It is evident 

 that the origin of sex, as that of species, is in some way de- 

 pendent on physical laws. Mrs. Treat and Mr. Riley dis- 

 cuss the subject in the American Naturalist. The former 



