vi VASCULAE SYSTEM 427 



The fluid is peopled|by amoeboid corpuscles but is without the red 

 corpuscles which have no power to escape through the walls of the 

 blood-vessels. 



Our present knowledge of the ontogeny of the lymphatic system 

 is in great part due to the labours of Huntington and McClure 

 whose papers should be consulted as regards details. It seems clear 

 that as a general rule lymphatic channels develop, later than the 

 blood - vessels, as intercellular chinks in the mesenchyme which 

 become continuous and form definite channels, the bounding cells 

 becoming converted into thin endothelium. 



Spleen. — The spleen arises in Lepidosiren and Protopterus (Bryce, 

 1905 ; Purser, 1917), which may be taken as typical examples, in the 

 form of a condensation of the mesenchyme of the gut-wall. Blood 

 spaces soon make their appearance in the rudiment which later 

 becomes intercalated in the course of the main venous channel leading 

 from intestine to liver. Later on the main blood-stream passes to 

 the liver by a direct channel, the spleen now lying on a lateral loop : 

 later still the afferent part of this loop becomes replaced functionally 

 by a new arterial connexion. 



The spleen rudiment frequently arises in close proximity to that of 

 the pancreas and this has led to statements that the spleen is actually 

 derived from the pancreas but the probability seems to be that 

 such statements are based upon erroneous observation. 



LITERATURE 



Allis. Zool. Jalirb. (Anat.), xiv", 1900. 

 Bemmelen, van. Zool. Anzeiger, ix, 1886. 

 Bemmelen, van. Meded. tot de dierkunde. Amsterdam, 1887. 

 Boas. Morph. Jahrb., vii, 1882. 

 Bryce. Trans. Roy. Soc. Edin., xli, 1905. 

 Choronshitzky. Anat. Hefte (Arb. ), xiii, 1900. 

 Dohrn. Mitt. Zool. Stat. Neapel, vii, 1886. 

 Dohrn. Mitt. Zool. Stat. Neapel, viii, 1888. 

 Evans. Amer. Journ. Anat., ix, 1909. 

 Gegenbaur. Jenaischer Zeitschrift, ii, 1866. 



Goette. Abhandlungen zur Entwickelungsgeschiclite der Tiere, v. Hamburg and 

 Leipzig, 1890. 



Greil. Morph. Jalirb., xxxi, 1903. 



Hoohstetter. Morph. Jahrb., xiii, 1888. 



Hoehstetter. Morph. Jahrb., xvi, 1890. 



Hoohstetter. Morph. Jahrb., xix, 1892. 



Hoehstetter. Hertwigs Handbuch der Entwicklungslehre, iii, 1906. 



Hoohstetter. Voeltzkows Wissenschaftliche Ergebnisse, iv. Stuttgart, 1906*. 



Hoffmann. Morph. Jahrb., xx, 1893. 



Hoyer. Bull, intern. Acad. Sci. Cracovie. Comptes rendus des Seances, 1900. 



Huntington and others. Anat. Record, ii, 1908. 



Huntington. Anat. Record, iv, 1910. 



Kellioott. Memoirs N.Y. Acad. Sci., ii, 1905. 



Kerr, Graham. The work of J. S. Budgett. Cambridge, 1907. 



Kerr, Graham. Proc. Roy. Phys. Soc. Edin., xvii, 1907* 



Kerr, Graham. Proc. Roy. Phys. Soc. Edin., xviii, 1910. 



Langer. Morph. Jahrb., xxi, 1894. 



Mackay. Phil. Trans. Roy. Soc, B, clxxix, 1889. 



