THE ANATOMY. BLOOD-GLANDS 



77 



blood away from the ventral vessel to the parietes. 

 There are thus two sets of vessels which convey blood 

 to the integument — the dorso-integumentary and the 

 ventro-integumentary. From the integument a series of 

 intestino-integumentary vessels again returns the blood 

 to the intestinal network, whence, as before stated, it 

 reaches the dorsal vessel. 



Fig. 21. 



VII. Blood-Glands. 



Connected with the vascular system there are in 

 several OHgochaeta structures which seem to be of 

 a glandular nature. Such structures occur in the En- 

 chytraeidae, the Lumbriculidae, the genus Phreodrilus, 

 the Perichaetidae, and perhaps the Eudrilidae. 



It will be convenient to commence with a descrip- 

 tion of these various organs in the groups mentioned, 

 before discussing the morphology and the functions 

 which they may perform. 



In the Enchytraeidae the dorsal vessel sometimes 

 contains a cellular rod which has been named the 

 'Herzkorper' by Michaelsen (woodcut, fig. 22). It 

 was described first in the genus Mesenchytraeus 

 (Michaelsen), where it consists of a solid rod of 

 cells attached to the ventral side of the dorsal blood- 

 vessel, and extending along its whole length; 'in M. 

 mirabilis and M. primaevus it is thick with irregular, 

 often strong swellings multicellular in section. In 

 M. falciformis, M. beumeri, and M. flavidus, it is 

 thinner, quite smooth, with only feeble swellings, and 

 in section shows only a few cells.' The organ is figured 

 by Michaelsen. In a later paper the same organ was 

 described in Stercutus. It has been justly compared by 

 him to the cardiac body of certain Polychaetes, such 

 as Pectinaria belgica, and a few others. As to its 

 function it was suggested by Michaelsen that it served 

 to ease the contractions of the dorsal vessel ; he pointed 



— v.t 



PONTOSCOLEX. CHIEF TRUNKS 



OF vasculae system. 



(After Perrier.) 

 V. d., V. m. Dorsal vessel. c. I. Con- 

 tractile heart, c. i. Intestinal heart, -y. i 

 Supra^intestinal vessel. v. I. Lateral 

 vessel. V. 8. Ventral vessel, v. t. Peri-intes- 

 tinal vessel, t.r., i.t. Smaller branches 

 of ventral vessel. 



