176 



OLIGOCHAETA 



Group APHANEURA. 



Family AEOLOSOMATIDAE. 

 As there is only one certainly known genus, viz. Aeolosoma, I do not attempt 

 a definition of the family. 



Genus Aeolosoma, Ehrenberg. 



Syn. Aeolosoma, Ehrenberg. Aeolonais, Gervais. Ghaetodermos, Leidy. 



Dbpibtitioit. Freshwater Oligoehaeta of small size ; segmentation not marked by- 

 regular septa ; prostomium ciliated ventrally ; setae in four bundles of one 

 to six setae each, usually capilliform (only sometimes both capilliform and 

 sigmoid). Clitellum developed only on ventral side of segments v-vii; testis 

 single in v ; ovary single in vi ; no differentiated sperm-duets ; oviduct 

 a ventral median pore in vi. Spermathecae in some or all of segments iii-iv. 

 Ifervous system represented by cerebral ganglia only. Lateral ciliated pits 

 present. 



Fig. 35- 



AEOLOSOMA EHEENBERGl. 

 (After Lankester.) 

 A chain of two individuals. 



This genus comprises a few species 

 which are distributed over Europe, W. Asia, 

 N. Africa, N. America, Central America, 

 (New Granada), India, and Africa, in fresh 

 water. They are all of small size, the 

 largest species, A. tenehrarum, reaching a 

 length of only lo mm. They are transparent 

 worms, with a very ' loose and uncertain 

 outline, the body flowing in various directions 

 in a very strange liquid fashion.' The seg- 

 mentation is not very marked externally, 

 except by the implantation of the setae. 

 When an AeolosoTna is fully extended the 

 head segment is separated from the next by 

 a constriction. The number of segments in 

 an individual is small, not more than a dozen 

 to fifteen. The prostomium is large, and 

 is ciliated upon the under surface ; on either 

 side are a pair of ciliated pits, which are 



