96 SOME SUGGESTIONS FOR BIRD STUDY. 



lightest part with the germ above lies towards the upper 

 side, that is nearest to the warmth of the hen's body 

 during incubation (Fig. 24) . 



At this point it is well to emphasise the distinction 

 between the germ on the one hand microscopic, living, 

 essential ; on the other all the rest, bulking large, but 

 after all, not living, accessory. 



Lastly, a brief note might be added on the breathing of 

 the chick within the egg by means of a special structure 

 which lies against the shell, on the use of the air chamber 

 where the chick first fills its lungs preparatory to " break- 

 ing out" and on the "egg tooth" (a limy nodule on the tip 

 of the bill) by means of which some birds effect their exit. 



In calling attention to the structural arrangements 

 enumerated above it ought to be possible to educe from 

 the pupils their significance in a good many instances. 

 Questions should be asked, e.g. upon the following points : 

 The use of the shell why eggs are narrower at one 

 end why egg-shells are porous the uses of the shell 

 membranes the use of the yolk the uses of the chalazae 

 why hens turn their eggs how chicks breathe within 

 the egg. 



STRUCTURAL STUDIES. 



For senior classes the adaptational features in a bird's 

 body will be found to yield an admirable series of lessons. 

 For this purpose the pupils under the guidance of the 

 teacher should mount upon a card examples of different 

 types of feather from various regions of the body. Cards 

 of the plumage of different kinds of birds should be made 

 as opportunity arises, and the best of these retained for 

 the school collection. A series of different types of bill 

 and foot might also be got together in course of time. 



A preparation of the wing of a bird, say of rook or 

 wood pigeon or of any small bird available, should be 

 made in the following way. On a flat board stretch the 

 fresh wing out fully, inner side downward. Endeavour to 

 keep the feathers unruffled and in their natural positions. 

 A small staple should next be driven through into the 



