DESCRIPTIONS OF EARTHWORMS. 83 



On the circulation of the blood in earthworms. 



In a paper recently published »0n Megascolex coeruleus''' 

 (Quart. Journal of Microsc. Science, Vol. XXXII, p. 49, 

 pi. VI — IX) Mr. A. G. Bourne gives a detailed account 

 of the vascular system of this gigantic earthworm. Upon 

 these observations, partially made in the living animal, 

 the author bases a theory about the probable course of 

 the blood in this worm, and concludes »that throughout 

 the body blood is forced from the contractile vessels into 

 peripherical networks; thence it is conveyed by a system 

 of intestino-tegumentary vessels to intestinal capillaries , 

 and from these it returns to the contractile vessels." It 

 seems to be unknown to Mr. Bourne, that about twelve 

 years ago I put forward the same view as his with regard 

 to the main question of the circulation in earthworms: 

 whence comes the blood into the dorsal vessel? In my pa- 

 per »Aanteekeningen op de anatomie van Lumbricus ter- 

 restris" (Tydschrift der Nederl. Dierkund. Vereeniging. Dl. 

 Ill, pi. 6) he will find on page 37: »As to the direction 

 of the course of the blood all observers agree in this point, 

 that the blood flows in the dorsal vessel from the poste- 

 rior extremity forwards, in the commissural vessels from 

 the dorsal side downwards, and in both ventral vessels 

 (supra- and sub-neural vessel) from the anterior extremity 

 backwards. The integumentary vessels are usually consi- 

 dered to be the afferent vessels, the intestinal vessels to be 

 the efferent vessels of the dorsal trunc. Because the skin is the 

 respiratory-apparatus of Lumbricus , the dorsal vessel should 

 be supplied with arterial blood and to be considered as a 

 specimen of aorta , whilst the venous blood , coming from 

 the intestinal canal , should flow to the ventral vessel , 

 which therefore should be comparable with the vena cava. 

 This opinion is also maintained and elaborated by Perrier 

 in his detailed description of the circulation in Urochaeta. 

 However I cannot agree with this view. First 

 it must be stated , that the vessel vt' (a branch of the 



^otes from tlie Leyden Mixsenm, Vol. XUI. 



