Development and Circulation of the Myriapoda. 371 



the cavities of the cells, thus constituting a vis-a-teryo, which con- 

 tributes to propel the blood onwards in its circulation through the 

 liver. Should there arise, however, any obstructing cause which the 

 resilience of the spleen is unable to overcome, a regurgitation must 

 take place, leading to a congestion both in the mesenteric and splenic 

 veins. The spleen may thus serve as a receptacle for the blood of 

 the abdominal circulation during any temporary check to its free 

 passage into the vena cava ; a purpose which is more fully answered 

 in herbivorous animals in whom the abdominal circulation is more 

 extensive, and the spleen is of larger dimensions and greater elas- 

 ticity. 



The splenic corpuscles are thickly scattered throughout the cellu- 

 lar parenchyma of this organ ; and from each corpuscle there arises 

 a minute lymphatic vessel; the interlacing of adjacent lymphatics 

 giving rise to a fine and extensive net-work. The trunks of these 

 vessels enter into the Malpighian glands, and again ramifying, form 

 a lymphatic plexus in the interior of these bodies. The fluid con- 

 tents of these vessels, which had been before pellucid, is now found 

 to contain white organic globules, similar in every respect to those 

 observed in the fluid of lymphatic glands in other parts of the body. 

 The author considers the secretion of this fluid, which appears to be 

 identical with the contents of the lymphatic glands, as being the 

 peculiar function of the splenic parenchyma. 



A few illustrative drawings and diagrams accompany this paper. 



2. "On the Structure and Developement of the Nervous and Circu- 

 latory Systems, and on the existence of a complete Circulation of the 

 Blood in Vessels in the Myriapoda and the Macrourous Arachnida." 

 By George Newport, Esq. Communicated by P. M. Roget, M.D, 

 Sec. R.S. 



This paper is the first of a series which the author proposes to 

 submit to the Royal Society on the comparative anatomy and the 

 developement of the nervous and circulatory systems in articulated 

 animals. Its purpose is, in the first place, to investigate the minute 

 anatomy of the nervous system in the Myriapoda and the Macrou- 

 rous Arachnida, and more especially with reference to the structure 

 of the nervous cord and its ganglia ; and thence to deduce certain 

 conclusions with respect to the physiology of that system and the 

 reflex movements in vertebrated animals ; secondly, to demonstrate 

 the existence of a complete system of circulatory vessels in the 

 Myriapoda and Arachnida ; and thirdly, to point out the identity of 

 the laws which regulate the developement of the nervous and circu- 

 latory systems throughout the whole of the Articulata, and the de- 

 pendence of these systems on the changes which take place in the 

 muscular and tegumentary structures of the body, as, in a former 

 paper, he showed was the case with regard to the changes occurring 

 in the nervous system of true insects. 



The first part of the paper relates to the nervous system. A de- 

 scription is given of this system in the Chilognatha, which the au- 

 thor was led, by his former investigations, to regard as the lowest 

 order of the Myriapoda, and approximating most nearly to the 



2B2 



