REPRODUCTION 



the lobster under its tail. The eggs of many spiders 

 are enveloped in a silken cocoon, which the mother 

 guards with jealous care. Insects, as flies and moths, 

 deposit their eggs where the larva, as soon as born, can 

 procure its own food. Most fishes allow their spawn, 

 or roe, to float in the water ; but a few build a kind of 

 flat nest in the sand or mud, hovering over the eggs 

 until they are hatched ; while the Acara of the Amazon 

 carries them in its mouth. The amphibians, generally, 

 envelop their eggs in a gelatinous mass, which they 

 leave to the elements ; but the female of the Surinam 

 toad carries hers on her back, where they are placed by 

 the male. The great Amazon turtles lay their eggs in 

 holes two feet deep, in the sand ; while the alligators 

 simply cover theirs with a few leaves and sticks. 

 Nearly all birds build nests, those of the perchers being 

 most elaborate, as their chicks are dependent for a 

 time on the parent. 163 The young of marsupials, as the 

 kangaroo, which are born in an extremely immature 

 state, are nourished in a pouch outside of the body. 

 But the embryo of all other mammals is developed 

 within the parent to a more perfect condition, by means 

 of a special organ, the placenta. It is a general law, 

 that animals receiving in the embryo states the longest 

 and most constant parental care ultimately attain the 

 highest grade of development. 



The Protozoa, which have no true eggs, have a sort 

 of reproduction called conjugation. In this process two 

 individuals unite into one mass, surround themselves 

 with a case, in which they divide into several parts, 

 each portion becoming a new individual, or the process 

 may be followed by repeated divisions of the two 

 individuals which separate as soon as the process is 

 finished, as in Paramecitim, or remain fused together, as 

 in Vorticella. 



