ZOOLOGY A\D BOTANY, MICROSCOPY, ETC. L27 



variation in size and shape of egg are probably purely physiological, and 

 in no direct or immediate way. if at all, related to the action of natural 

 selection. A study of Lntra-in dividual variation indicates that the 

 relative variability of eggs is a definite characteristic of the individual. 



Development and Evolution of Lungs.* — M. Makuschok has 

 studied the development of the lungs in the nurse-frog, Alytes obstetricans, 

 which agrees with other Amphibians investigated (frog, toad, newt, 

 salamander, etc.). The primordia of the lungs appear as very minute 

 depressions in the posterior portion of the branchial region. They 

 never appear in Alytes before the completion of the fifth gill-pocket, 

 but there are differences in this respect between the various Amphibian 

 types. In the Axolotl the six pouches appear in order, and then the 

 lung-prim ordia ; in the newt the sixth pair of pouches and the lung- 

 primordia appear almost simultaneously ; in Bomhinator the sixth pair 

 appear after the lung-primordia. This may be because the sixth pair of 

 pouches are soon reduced to mere vestiges — the post-branchial bodies. 

 and it is well-known that vestigial structures tend to have a belated 

 appearance in ontogeny. 



The appearance of the lung-primordia after the sixth gill-pouch 

 is what might be expected if the lungs are serially homologous with 

 gill-pouches. Their early stages and their relation to the gut are closely 

 alike. Soon after their appearance the lung-primodia are separated off 

 from the branchial region — slowly in Alytes, quickly in other Amphibia. 

 The post-branchial cavity becomes the laryngo- tracheal cavity, com- 

 municating with the definitive branchial cavity by a minute slit. This 

 slit defines the posterior border of the branchial cavity and the anterior 

 end of the oesophagus. If the lungs have had a developmental connexion 

 with the hepatic diverticulum, they lose it when they are separated off 

 from the gut. 



The author supports Goette's view that the lungs are derivatives of 

 the last (the seventh) pair of gill-pouches. He regards Crossopterygii 

 and Dipnoi as types which remained by the way while their relatives 

 (Pro-Pulmonata) pressed on towards terrestrial and tetrapodous and lung- 

 breatbing existence. 



Development of Feathers.f — Raymond Pearl and Alice M. Boring 

 have studied the regeneration of feathers, comparing the patterns in the 

 regenerates and in the originals. In order to follow particular follicles 

 they made tattoo circles round them. It is known that the barred 

 pattern of some fowls, e.g. Barred Plymouth Rock, behaves in a clean- 

 cut Mendelian manner, and seems to be represented by a single Mendelian 

 factor or gene. 



1. In the general body plumage a feather is not usually regenerated 

 m< >re than three times, the follicle remaining quiescent. Wing primaries 

 have the maximum regenerative capacity. 



2. A follicle that has been absolutely inactive for a long period 

 (e.g. six months) preceding the natural autumn moult produces a new 



* Anat. Anzeig., xlvi. (1914) pp. 497-514 (8 figs.). 

 t Science, xxxix. (1914) pp. 143-4. 



