354 The Systematic Study of Annelids. [July, 



through the prater. In Eunice, Nerine, and Arenicola branchial 

 filaments are developed in connection with the foot, in which the 

 red fluid of the worm circulates. In Syllis the cirri are very long 

 and moniliform, attaining in a kindred genus, Guttiola, a length 

 considerably greater than that of the worm's body, to which they 

 seem attached like so many Gorgon's locks. In Polyojjthalmus an 

 eye is developed on each foot. The further modification of these 

 parts leads to very numerous minor generic divisions, all resting 

 mainly upon differences in the form of the appendages and setae of 

 the foot, and only to be discovered by attentive and careful examin- 

 ation with the microscope. 



Various forms of setae are drawn in Figs. 14, 16, 17, 18, belonging 

 respectively to Sabellaria, Praxilla, Leprea, and Leucodore, and all 

 equally characteristic of the genera and species to which they belong. 



The Oligochaeta (fresh- water worms) have not received even as 

 much attention as the Polychaeta (the marine), and indeed this is 

 not surprising, for without the use of a microscope applied to the 

 setae, it is impossible to distinguish some of the species with any 

 certainty. Much has yet to be done with this group of Annelids ; 

 for it has not at present been touched upon by Kinberg, Ehlers, or 

 Malmgren. The setae are fewer in number in this group (whence its 

 name) than in the one we first looked at, and there are no appen- 

 dages in the form of feet ; hence the setae become of still greater 

 importance to the zoologist. 



In some species (Tubifex) the setae are hair-like bodies; in 

 others they are stout and short (Lumbricus, Phreoryctes) , Fig. 20, 21 ; 

 in others again they have a bind apex (Clisetog aster), Fig. 24 ; or this 

 sort of setae may be associated with other hair-like ones (Clitellio, 

 &c), Figs. 22 and 23 ; in Ctenodrilus the setae are pectinated, Fig.25. 



There are many species of Oligochaeta, though the group is far 

 less numerous than the Polychaeta. They are to be found in moist 

 earth, in the ooze of streams and rivers, and in sandy soils also. 

 Some writers contend that no Oligochaeta are marine, whilst it is cer- 

 tain that no Polychaeta are fresh- water or terrestrial. 



The geographical distribution of Chaetopods is a matter of which 

 very little is known, Schmarda's and Kinberg's works being the 

 principal sources of information, whilst M. de Quatrefage's volumes 

 contain figures and descriptions of many foreign species. It appears 

 that very many genera are cosmopolitan and apparently some spe- 

 cies ; but on this matter we must hope for sounder information 

 when we have students of Annelids as ardent and numerous as our 

 entomologists, ornithologists, and other specialists. 



The study of the development and anatomy of the Chaetopods 

 does not belong to the specialist, and whilst it no doubt has a higher 

 importance than the mere recognition of specific differences, cannot 

 supersede such work. There are many men whose minds are so 



