DESCRIPTIONS OF GENERA AND SPECIES 



241 



Very characteristic of the genera Ilyodrilus, Branchiura, and apparently Telmato- 

 drilus, is the existence of 



an integumental network 

 of which also traces exist in 

 Lininodrilus. This, again, 

 is a character which brings 

 the Tubificidae into relation 

 with the higher Oligochaeta. 

 For the details of the circu- 

 latory system the reader is 

 referred to the descriptions 

 of the several genera. 



The two species, Bran- 

 chiura sowerhii, and Hes- 

 perodrilus hrancMatus are 

 remarkable for the possession 

 of branchial processes ; these 

 are paired structures, either 

 dorsal and ventral [Bran- 

 chiura), or lateral (Hespero- 

 drilus) in position. They 

 are found only upon the 

 posterior segments of the 

 body. Their structure has 

 been dealt with above. 



The Tubificidae may be 

 divided into two sections, 

 according as to whether the 

 brown ovoid gland, so charac- 

 teristic of the Naids, is or is 

 not present. In the following 

 genera it is present : — 



Ilyodrilus. 

 Bothrioneuron. 



Fig. 42. 



Fig. 41. 



LOPHOCHAETA. VASCULAR 



SYSTEM OF SOME OF THE 



ANTEEIOK SEGMENTS. 



(After Stole.) 



I. Ventral vessel. 2-6. Vessels 

 joining intestinal network. 7. Slen- 

 der posterior part of ventral vessel 

 just after it joins; 12. Snb-intestinal 

 vessel. 9, 13. Intestinal hearts. 15, ■ 

 16. Commissural vessels. 17. Dorsal 

 vessel. , 



BOTHHIONEUEON VASCULAR 



SYSTEM. 



(After Stole.) 



I~IX, Segments. 1-6. Lateral 

 hearts. 7. Ventral vessel. 8. Pha- 

 rynx. 9-14. Vessels supplying in- 

 testinal network. 15. Sub-intestinal 

 vessel. 16-19. Vessels supplying in- 

 testinal network. iS, 21. Intestinal 

 hearts. 22, Supra-intestinal vessel. 

 23. Dorsal vessel 



B 



In all the others it is absent ; 



Stolc has figured these structures in the two genera mentioned, and his figures are 



I i 



