294 REPRODICTION IN ANIMALS 



stricts its base and, separating from the parent, leads 

 an independent life thereafter. 



In many sponges small buds develop on the inside 

 of the body and with the death of the parent, or even 

 before, become freed and grow into the adult condition. 



Among the worms, especially the jonited or segmented 

 worms related to the earthworm, there are many striking 

 examples of budding. In certain species the body 

 develops a head near the middle after which the hinder 

 portion with the new head becomes detached as a new 

 individual and swims away. In the case of the palolo 

 worm of the Fiji and Samoan islands this hinder section 

 never develops a head, yet it swims about in the fall 

 months in countless numbers, and is collected as a highly 

 prized article of food. 



Fig. 69. — Budding in a Marine Worm. 



Fission. — Fission, or the equal division of an organism 

 into two daughter individuals, is a widespread mode of 

 asexual reproduction with the lower animals. Among 

 the unicellular organisms, for example, it is undoubtedly 

 the most common method of multiplication. In the 

 amoeba, that may be taken as a type, the nucleus first 

 divides, and then the cell protoplasm gradually draws 

 apart until the connecting strand separates and two off- 

 spring thus arise. In the sea anemone, related to hydra, 

 the body occasionally divides into equal parts, and among 

 certain small species of flatworms fission appears to 

 occur whenever there is abundant nourishment. 



In all these cases, and others that might be cited, the 

 half-sized descendants grow to the size of the original 

 parent, and repeat the process if conditions are favorable. 



