ANIMAL PRODUCTION. 463 



discussion of recent investigations which have to do with the occurrence of 

 free su^iir in the blood. A polemical article. 



International catalogue of scientific literature. Q — Physiolog'y {Intcniat. 

 Cut. ISci. Lit., 5 (Jimi), pts. 1. III). VlII-\-S,i!); 2, pp. i095).— The bibliography 

 of physiology, including experimental psychology, pharmacology, and experi- 

 mental pathology, is continued in this volume of the international catalogue 

 (E. S. li.. IG, p. 689). Part 1 is the author catalogue and part 2 the subject 

 catalogue. The present volume contains material received between May, 1905, 

 and May, 1900. 



ANIMAL PRODUCTION. 



Some observations and experiments on the natural and artificial incuba- 

 tion of the egg' of the common fowl, A. C. Eycleshymer {Biol. Bui. Mar. 

 Biol. Lab. Woods IIoll, 12 {J 907), No. 6, pp. 360-37 Jf).— A series of experiments 

 on the developing chick showed that frequently variations in development were 

 so great that the value of the results was materially decreased. The author 

 attempted, therefore, to secure additional data i-egarding the effect of the posi- 

 tion of the egg. turning the egg, cooling, ventilation, and moisture of the air. 



Special attempts were made to secure uniformity with respect to size and 

 other conditions in the Plymouth liock eggs used. The eggs were tested by 

 transmitted sunlight, and those in the same stage of development were selected 

 for experimental purposes. 



In tests undertaken to ascertain what position eggs occupy during natural 

 incubation it was found that an oblique position was usual, but that this was 

 a factor of little or no importance. The observations and experiments with ar- 

 tificial incubation on the other hand led to the deduction that when the supply 

 of fresh air (oxygen) is inadequate tlie oblique position of the egg with the 

 small end up brings the embryo in closer contact with the air chamber and is 

 decidedly advantageous. When there is an abundant supply of fresh air there 

 is little to gain in placing the eggs obliquely. 



As shown by observations with nests having felt sides and concave glass 

 bottoms, eggs are turned partially or completely by hens at least five times 

 during any given day, which is much more frequently than has been supposed. 

 "The hen turns the eggs in two ways. If a sitting hen be watched as she re- 

 turns from feeding to sitting, it will be seen that she moves her body rapidly 

 from side to side. Whether the object be to turn the eggs is uncertain. Prob- 

 ably the first object is to bring the surface of the body in the closest possible 

 contact with the growing embryos. Accidentally or purposely she also turns 

 the eggs. This is not only true of the hen returning from feeding, but also 

 when on the nest, for she is frequently observed moving about and settling down 

 with the same characteristic lateral movements. Sometimes there are so many 

 eggs in the nest or they are so widely scattered that the hen fails to projierly 

 cover them. When such conditions occur the hen invariably uses her beak to 

 bring the outlying eggs in contact with her body. Not only does she frequently 

 thus turn the eggs, but also she very often reaches beneath her body and turns 

 the eggs lying near the center of the nest. Why she does this is a question 

 which awaits an answer." The experiments made with incubators indicated 

 that frequent turnings, at least five, gave the best results. 



In a study of the temperature of eggs with reference to incubation, a series 

 of observations is reported on the daily temperature of hens. Special self-regis- 

 tering thermometei-s fastened to blocks with the upper surface egg-shaped, 

 which were placed under the hens in the nests, were used, and also thermome- 



