AVES 



407 



sented. Much of the time given to the practical studies of the 

 group of birds should be directed to tjjeir life and adaptations. 



Fig. 205. 



Fig. 206. 



•opO/n_.' 



•po- 



•;-o 



Fig. 205. Diagram of the female genital organs of a Bird, t, cloaca; *, intestine; k. kidney; 

 o, ovary with ova of different size; od., oviduct; o./., funnel 01 the oviduct; 0.0., opening of the ovi- 

 duct into the cloaca; u, ureter; u.o,, opening of ureter into the cloaca. Only one ovary and oviduct 

 are fully developed in the Birds. 



Questions on the figure. — What openings has the oviduct? Why must the 

 union of sperm and ovum take place before the egg gets well down the oviduct? 

 Define the cloaca. On which side are the sexual organs rudimentary in the female 

 bird? 



Fig. 206. Diagram of the urino-genital organs of a male Bird, ad., adrenal body; c, cloaca; 

 i, intestine; k, kidney; t, testis; u, ureter; u,o,, opening of ureter into the cloaca; v.d.t vas deferens; 

 v.d.o.t opening of the vas deferens; v.s., vesicula seminalis. 



Questions on the figure. — What is the function of the vas deferens? Of the 

 vesicula seminalis? What differentiates the cloaca from the intestine? What 

 are the chief differences in the excretory organs of birds and mammals ? 



These various habits and modes of life have frequently been 

 made the basis of classification: for example, some fly and 

 some do not; some wade, having long legs; others swim and 



