REPRODUCTION 



231 



anterior end of the body with a tiny brain just above the pharynx 

 in the third anterior body segment. 



Reproduction. The earthworm has both male and female sex 

 cells present in its body and hence is said to be hermaphroditic 

 (her-mafro-dlt'ik). In order to have the eggs fertilized when 

 they are laid a mutual exchange of sperm cells takes place between 

 two worms, the sperms being placed in four little sacs on the under 

 side of each worm. 

 Later a swollen 

 area called the cli- 

 tellum (about one 

 third the distance 

 from the anterior 

 end) forms a girdle 

 which, as it passes 

 toward the anterior 

 end of the earth- 

 worm, receives 

 from body open- 

 ings the eggs, the 

 sperms received 

 from the other 

 earthworm, and a 

 nutritive fluid in 

 which the eggs live. 

 The fertilized eggs 

 are then left to 

 hatch. The bags or cocoons may be found in manure heaps or 

 under stones, in May or June. 



Practical Exercise 6. What worms are found in your locality ? Are there 

 any useful ones? Any harmful ones? What is the difference between a 

 worm and a caterpillar? 



Self-Testing Exercise 



Check the true statements in your workbook. 



T. F.- 1. Invertebrates have a backbone and an internal skeleton. 



T. F. 2. Protozoa are single-celled animals. 



T. F. 3. Sponges live only in the ocean. 





^®, sperms 



eggs are fertilijed,^ 



JN^S /"embryos 



^— J ^~\_ Capsule 



A secretion, given off by the clitellum of the earthworm, hardens, 

 forming a cocoon or girdle which surrounds the body. What is 

 the use of this girdle ? 



