. Biology; the story of living things. 48 NATURAL HISTORY. Huijh Spiricer A spider with its egg cocoon. until large enough to care for themselves. The male of the so-called midwife toad (Alytes) carries the eggs entangled around the legs. The male Surinam toad places the eggs on the back of the female, where each sinks into a tiny pouch as it develops. Animals that lay eggs which hatch outside of the mother's body are said to be oviparous. A modified form of this procedure is seen in some nematodes, arthropods, fish, amphibia, and reptiles. Here the eggs remain in the oviduct or uterus of the
. Biology; the story of living things. 48 NATURAL HISTORY. Huijh Spiricer A spider with its egg cocoon. until large enough to care for themselves. The male of the so-called midwife toad (Alytes) carries the eggs entangled around the legs. The male Surinam toad places the eggs on the back of the female, where each sinks into a tiny pouch as it develops. Animals that lay eggs which hatch outside of the mother's body are said to be oviparous. A modified form of this procedure is seen in some nematodes, arthropods, fish, amphibia, and reptiles. Here the eggs remain in the oviduct or uterus of the mother until they are almost ready to hatch, the body of the mother acting as an incubator. Such forms are said to be ovoviparous. Most of the mammals which retain the eggs in the body until the young are born are said to be viviparous. Here the young are held as embryos within the body of the mother and nourished by means of an organ called the placenta. The young of mammals are suckled at the breasts of the mother until they are able to eat solid food. Relations of Mutual Aid A certain amount of protection is afforded plants from their habit of living in communities. Examples are the aggregations of cacti in our western deserts or the acacia and "thorn bush" communities of Australia. The animal world, too, shows many examples of protec- tion among gregarious forms. The schooling of fishes not only is a defense for the group from larger fish, but it also enables small fish, working concertedly, to prey on organisms much larger than them- selves. The driver ants in Africa, traveling in great swarms, often overcome and devour animals hundreds of times larger than them- selves. Wolves hunt in packs, several of them rushing together to bring down their larger prey. Deer and other herbivorous animals move in herds for mutual protection. Another relation of mutual aid results from the development of division of labor among certain animals. Although social division of labor
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