ANNELIDA OR ANNULATA 



105 



and sperm into a cocoon, which is secreted by the modified clitellum. 

 There is no metamorphosis. The oligochaetes are singularly lacking 

 in sense organs, pigment eyes being found in the Naids. We shall 

 mention only five of the eleven families. (Figure 44.) 



Aelosomatidae are microscopic fresh water worms, whose red, 

 yellow and brown oil globules make them appear spotted. They 

 reproduce by fission, and 

 are considered the most 

 primitive oligochaetes. 



Enchytraeidae are slender 

 small worms found in plants 

 and in fresh water, near the 

 sea shore. Their blood may 

 be colorless, red or yellowo 

 The small white form, 

 Enchytraeus albidus^ is re- 

 commended by Gamble as 

 exceedingly useful for obser- 

 vation under a binocular 

 microscope. It requires a 

 temperature not higher than 

 60° F. 



Naidae are small, trans- 

 parent, aquatic forms with 

 a distinct head, and from 



two to four groups of setae on each segment. In Nais^ a common 

 fresh water species, the blood is yellow or red. Eyes are usually 

 present. Budding is a common form of reproduction. The Tubifi- 

 cidae are slender reddish worms living in tubes, from which they 

 protrude the posterior end into the water. Many species of Tubifex 

 are found in brackish water; a few occupy fresh. 



Lumbricidae include the common earthworms. Among them 

 are the familiar Lu7nbricus terrestris of Europe and America; 

 Eisenia {Allolobophora) foetida, commonly found in manure; and 

 Helodrilus^ represented in America by ten species. Aristotle called 

 the earthworms the " intestines of the earth." 



Order 2. Oligochaeta. Fam. Lumbricidae. Type — Lumbricus 

 terrestris. — The earthworm is from 5 to 18 inches long, with 100 to 

 160 segments, strongly marked by external rings. A tropical 

 species, Alegascolex australis^ reaches a length of eleven feet. 



Fig. 44. Nats. (From Leunis. Davenport's 

 Zoology. Courtesy of The Macmillan Co.) 



